Assign Fn/preview and AE-L/AF-L buttons problems

[posiview]

Hi, I've had my Fn button assigned to bracket burst for some time now, but for some reason it doesn't won't work anymore.

The above buttons works because I've used it with other functions, ie spot metering.

I've rest everything a few times ( green buttons), but no help.

Any advice would be appreciated.

Thanks.