SD card will not mount in MAC

Kell

Kell

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Kell
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I have a Mac that's maybe a year or so old. No problems up until very recently.

But it's now just refusing to access the card. Or any other card I tried.

For the record, the same SD card works in my PC and also in my work mac, so I don't think it's the card. Especially as when running Disk Utility, the card is visible (greyed out) but using 'mount' or 'first aid' doesn't remedy it. So my Mac obviously knows it's there, it just won't open.

It just says 'Not Mounted' but won't mount it.

sd-cards-will-not-mount-v0-d8771g1t2boh1.png



Things I've tried:

  1. Restarting Mac - no difference.
  2. Reformatting card in another Mac - no difference
  3. Reformatting card in PC - no difference
  4. Reformatting card in camera - no difference
  5. Ensuring all external drives are selected in finder - no difference
  6. Disk Utility: trying to mount the card from there - no difference
  7. DIsk Utility: First Aid - no difference
  8. Plug in SD card reader - no difference
  9. Check for Mac updates - no updates
  10. Tried another SD card - no difference
  11. used 'Terminal' app to try and locate and force quit a fsck error - didn't' show up in the way the instructions suggested


Googling it just seems to bring up downloadable software - and I don't want to start venturing down that route. Partly because, who do you trust and partly because I'm sure the solve is probably much simpler.

Anyone got any ideas of things I haven't tried?
 
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Does it show up in the Photos app to import the contents? I normally plug the camera in with the card in it as it seems to be more reliable than removing the card and trying to use it directly. USB devices on Macs are crap a lot of the time. I've had it ruin USB sticks and refuse to use them even though it wrote the thing. It's very poor.
 
srichards said:
Does it show up in the Photos app to import the contents? I normally plug the camera in with the card in it as it seems to be more reliable than removing the card and trying to use it directly. USB devices on Macs are crap a lot of the time. I've had it ruin USB sticks and refuse to use them even though it wrote the thing. It's very poor.
Click to expand...
I don't normally use the Photos app.

My workflow is normally - plug in the card, and copy the images to a folder called RAW. Then remove and replace in camera. I then use the RAW folder as my location when importing to LR.

I'm not entirely sure if I even have a data cable to connect this camera to the laptop.
 
I'm not at home to try anything, but this is what AI is currently suggesting:

My thought process
You've done an excellent job isolating the problem. Because the card works on other devices, another card fails on this Mac, and both the built-in slot and an external USB card reader exhibit the exact same behavior, we can draw a solid conclusion:

Your hardware is detecting the card, but macOS's background disk-mounting system (or a security permission) is hung or blocking the volume from loading.

Since Disk Utility sees the physical drive (greyed out) but fails when you click "Mount", you don't need any sketchy third-party software. The solution lies in resetting macOS's disk mounting services or security permissions.

Here are the step-by-step fixes, ordered from simplest to most thorough.

Step 1: Check "Allow Accessories to Connect"​

On recent macOS versions (Ventura, Sonoma, Sequoia), Apple added a security feature for MacBooks that blocks USB/SD card data lines until approved. Sometimes this setting glitches and allows the Mac to "see" the hardware in Disk Utility while blocking the actual data volume from mounting.

  1. Open System Settings > Privacy & Security.
  2. Scroll down to the Security section.
  3. Look for "Allow accessories to connect".
  4. Change it to "Automatically When Unlocked" (or if it's already set to that, switch it to "Ask Every Time", unplug the card, plug it back in, and click "Allow" on the prompt).

Step 2: Restart the Disk Arbitration Daemon (​

macOS uses a hidden background process called diskarbitrationd to manage disk mounts. If this process gets stuck in a loop, no external storage (SD cards, USB drives) will mount—even across restarts if the saved system state restores it.

  1. Unplug the SD card.
  2. Open Terminal (press Cmd + Space, type Terminal, hit Enter).
  3. Type the following command and press Enter:
bash
&nbsp; sudo killall diskarbitrationd<br>
  1. Enter your Mac admin password when prompted (the characters won't show as you type).
  2. (macOS automatically restarts this service in under a second).
  3. Also run these two commands to clear any stuck file system background helpers:
bash
&nbsp; sudo pkill -f fsck<br> &nbsp; sudo pkill -f mount<br>
  1. Plug your SD card back in and check if it mounts.

Step 3: Try Force-Mounting via Terminal​

Using the command line bypasses the Finder/Disk Utility interface and will give us a specific error code if it fails.

  1. Insert your SD card.
  2. Open Terminal and run:
bash
&nbsp; diskutil list<br>
  1. Look through the output for your SD card (it will usually be near the bottom, named something like /dev/disk2 or /dev/disk3, with a partition like disk2s1 or disk3s1).
  2. Run the mount command using your card's specific partition identifier:
bash
&nbsp; diskutil mount /dev/disk2s1<br>
(Replace <em>disk2s1</em> with your actual partition identifier). 5. If it fails, try mounting in Read-Only mode:

bash
&nbsp; diskutil mount readOnly /dev/disk2s1<br>
If Terminal gives you an error message (like "Resource busy" or "Permission denied"), take note of the wording—it pinpoints exactly what is holding the drive hostage.

Step 4: Boot into Safe Mode (Clears System Caches & Resets Daemons)​

Booting in Safe Mode runs a directory check on your Mac's internal drive, clears system caches, and prevents non-essential background processes from launching.

  • Apple Silicon (M1/M2/M3/M4): Shut down your Mac completely. Press and hold the Power button until "Loading startup options" appears. Select your main hard drive (Macintosh HD), hold the Shift key, and click "Continue in Safe Mode".
  • Intel Mac: Shut down. Turn it on and immediately press and hold the Shift key until the login screen appears.
Once logged into Safe Mode, test the SD card. If it mounts in Safe Mode, restart your Mac normally—the system cache reset often fixes the issue permanently for normal boots.

Step 5: Test in macOS Recovery Mode (The Ultimate Diagnostic)​

If none of the above works, test whether the card mounts inside macOS Recovery. This completely rules out any software glitch in your main user environment:

  1. Shut down your Mac.
  2. Apple Silicon: Press and hold the Power button until options appear, select Options, and click Continue.
    (Intel: Hold <em>Cmd + R</em> while powering on).
  3. Once in Recovery Mode, open Disk Utility from the menu.
  4. Plug in the SD card and see if you can click Mount.
  • If it mounts in Recovery Mode: The hardware is 100% fine. The issue on your main system is being caused by a background app, system extension, antivirus, or VPN installed on your Mac.
  • If it refuses to mount even in Recovery Mode across multiple ports and readers: The Mac's system controller firmware (SMC/NVRAM state on Intel, or system management controller on Apple Silicon) needs a hardware reset.

Summary Checklist:​

Try Step 1 and Step 2 first—restarting diskarbitrationd and checking accessory permissions solves this exact issue in over 90% of cases without needing any software downloads or reformatting! Let me know what you find or if Terminal gives a specific error code.
 
Not being a Mac user........I will throw in my tuppence worth......

Is there I difference between the two Macs in regard to their OS?

Does it make any difference if you have the SD card lock switch on or off?
 
Box Brownie said:
Not being a Mac user........I will throw in my tuppence worth......

Is there I difference between the two Macs in regard to their OS?

Does it make any difference if you have the SD card lock switch on or off?
Click to expand...

AFAIK, both macs are completely up-to-date - the OS on Macs is periodically updated and we're forced to update at work.
 
I had the same issue a few months ago but annoyingly I cannot remember how it was resolved. There were so many suggested solutions on the web, I tried several and it eventually worked. I do remember trying all the steps except the final one. It seems that IOS updates sometimes cause problems with USB connections. I have had the issue on more than one occasion.
 
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Brentor said:
I had the same issue a few months ago but annoyingly I cannot remember how it was resolved. There were so many suggested solutions on the web, I tried several and it eventually worked. I do remember trying all the steps except the final one. It seems that IOS updates sometimes cause problems with USB connections. I have had the issue on more than one occasion.
Click to expand...

Some of my googling suggests that as a possible cause, but also pulling out the card without properly ejecting it.

I am guilty of that as I've spent the past 20 years on PCs where it wasn't an issue. And I do forget a fair bit. But... up until now, it's been OK.
 
Brentor said:
Did you sort this?
Click to expand...
Not yet.

Thought it was going to work when I changed the accessories preferences in step one above. Now when I put the card in the MAC asks if I want to allow it to connect, but it still doesn't see it.

I do have a workaround as both my home and work macs, and PC are connected to the same One drive - so I can plug it in to my PC, upload them from there and access them on my MAC, but it's an extra step I'd rather not have to take.
 
Silly question but is the card locked. I lock all cards when I take them out of camera. Turns out the newer macOSs don’t like it and you have to unlock the card for it to mount
 
ictus said:
Silly question but is the card locked. I lock all cards when I take them out of camera. Turns out the newer macOSs don’t like it and you have to unlock the card for it to mount
Click to expand...
Not a silly question, but no, it's not locked.

As I say it opens on both my work mac and home PC, so I know there are no issues with the card.

THe two 'new' variables are a recent OS update and a new provider for a VPN service.

But I've tried turning off the VPN (as I have to to access this site) to no avail.

And I've tried everything on that list I got from AI. THe closest I got was step 5 - opening the mac in recovery mode - where it says the card is mounted. THen it simply won't do it in normal mode.

The added issue is that I have no clue what I'm doing. i.e. my IT knowledge is zero. So everything I'm trying, I don't really know what it's doing.

I think I might have to find a Mac hub somewhere, or take it in to work and ask our IT guys there if they can help.
 
No help at all but I'm watching this with interest as I have two external SSDs that I've got similar issues with.
 
Hadron said:
No help at all but I'm watching this with interest as I have two external SSDs that I've got similar issues with.
Click to expand...
Do they mount on other machines? I mean usually our general rule on drives is if they play up, then you stop using them for work, maybe secondary backup drives only. I know its a bit harder to run to these rules when drive prices have tripled in the last 6 months.

Some external drives will let DriveDX do a smart report on the drive (with the additional drivers) but not all support this. An NVMe in a case probably does, my T7 doesn't.
 
Jonnybrad2001 said:
Do they mount on other machines? I mean usually our general rule on drives is if they play up, then you stop using them for work, maybe secondary backup drives only. I know its a bit harder to run to these rules when drive prices have tripled in the last 6 months.

Some external drives will let DriveDX do a smart report on the drive (with the additional drivers) but not all support this. An NVMe in a case probably does, my T7 doesn't.
Click to expand...
They work fine on a Windows machine, as far as my Mac is concerned they don't exist.
 
OK - I think this MAY have solved it...

It's an Eset security extension. (My cyber security programme)

This is what finally solved it.

Solution 1: Disable ESET's Endpoint Security Extension in macOS Settings​

In macOS Ventura, Sonoma, or Sequoia, you can disable ESET's system extension directly:

  1. Open System Settings.
  2. Go to General > Login Items & Extensions.
  3. Scroll down to the bottom and find Extensions.
  4. Click the i (Info) icon next to Endpoint Security Extensions.
  5. Toggle OFF ESET Real-time File System Protection / ESET Endpoint Security.
  6. Do the same under Network Extensions if needed.
  7. Unplug your SD card and plug it back in. It should mount automatically on your Desktop!


I just need to restart it a few times to ensure that it continues to work. And then check that it the Cyber Security is still on:



Disabling that specific extension turns off ESET's Real-time File System Protection (the background watcher that inspects every file the moment it is opened or connected).

Your Web & Email Protection, Firewall, and manual virus scans in ESET are still 100% active.

If you need ESET's real-time file protection turned on for your Mac, you can turn it back on without it breaking your SD cards.

Here is how to configure ESET so you get full protection AND working SD cards:

Step 1: Tell ESET to leave Removable Media alone​

  1. Open the ESET application on your Mac.
  2. Press Cmd + , (Command + Comma) on your keyboard to open ESET Preferences / Settings.
  3. Go to Real-time File System Protection (or Detection Engine > File-System Protection).
  4. Under Media to scan, uncheck Removable media (or change "Action on removable media" to Do not scan).
  5. Close the preferences.

Step 2: Grant ESET "Full Disk Access" in macOS​

The reason ESET was locking up your SD card in the first place is that macOS was blocking ESET from reading the card sectors, causing ESET to freeze the drive in response.

  1. Go to System Settings > Privacy & Security > Full Disk Access.
  2. Make sure all ESET entries (ESET Cyber Security, ESET Real-time File System Protection, ESET Agent) are toggled ON.

Step 3: Turn the Extension back ON​

Now you can safely re-enable the extension:

  1. Go to System Settings > General > Login Items & Extensions > Extensions.
  2. Click the (i) icon next to ESET Real-time File System Protection.
  3. Turn the toggle back ON.

The Result:​

ESET will now be 100% fully active and protecting your Mac, but because we unchecked "Removable media", it will ignore SD cards and USB drives when you plug them in so they mount effortlessly!
 
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It's very odd as I've been running ESET for a number of years and not had this issue.

The only things that have changed just before this issue have been an OS update, and me realising that ESET came with a free VPN so I didn't need to pay for Nord any more - and installing the ESET version instead.

I'm pretty sure it's one of those two things causing the issue.
 
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