Turn off FileVault is grayed out.

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?

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?

Any luck?

Filevault state, open Terminal & paste these in…

    fdesetup status

    diskutil cs list | grep 'Conversion Progress'

Filevault state, open Terminal & paste these in…

    fdesetup status

    diskutil cs list | grep 'Conversion Progress'

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