Turn off FileVault is grayed out.

Filevault state, open Terminal & paste these in…

    fdesetup status

    diskutil cs list | grep 'Conversion Progress'

Hmmm,

Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?

Safe mode attempts to repair Disks & clears lots of caches, so if Safe Mode works try again in regular boot.

To find out if it's system wide or user specific, try this...

Open System Preferences>Users & Groups, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.

Does it work in the new account?

Any luck?

It must be done encrypting then, do you still the get Greyed out file decryption button?

I have the same problem with my late2011 MacBook Air

Greyed out file decryption button. Now OS updates will not install either.

I ran a disk utility first aid from the command R boot up. Startup was ok but numerous errors on the actual HD.

Also, no matter how often I try I cannot boot into safe mode anymore.

Any suggestions?

Thanks for your help

fdsetup status gets reply of FileVault is On.

FileVault master keychain appears to be installed

diskutil cs list | grep 'Conversion Progress' gets no response.

am i entering the values incorrectly?

Filevault state, open Terminal & paste these in…

    fdesetup status

    diskutil cs list | grep 'Conversion Progress'