If that doesn’t work, an Archive & Install may be needed. DiskWarrior is also worth a shot (this is by far my most used disk utility). Rebooting your Mac in Safe Mode can sometimes get things working well-enough that a second, normal reboot then works normally Hold down the Shift key at startup to boot in Safe Mode. It may also be having trouble accessing an internal or external hardware component, but this is less-likely. Instead macOS formats external FileVault drives as CoreStorage Logical Volumes formatted with Mac OS Extended (Journaled). What this means for us mortals is that when a Mac stalls at the Apple logo or the logo with a spinning gear, it probably has a corrupt Mac OS X installation. FileVault full-disk encryption uses XTS-AES-128 encryption with a 256-bit key to help prevent unauthorized access to the information on your startup disk. FileVault is a weird beastie that places files. Install DiskWarrior on a working Mac & enter key Use the Bootable disk wizard to create a bootable USB Rename the USB drive to DW & eject Insert USB into mac that needs to be repaired and power up mac while holding Apple + R Open Disk Utility Select drive and then select 'Unlock' & enter password to unlock Close Disk Utility Open. Shortly thereafter it transfers command to the almighty (and controversial) launchd process. Older Macbooks with spinning-rust hard drives running OS X: With the first version of FileVault enabled, no. Once the spinning gear appears the BSD kernel (Darwin) has assumed command and begins loading device drivers. There is a nice website that maybe helpful for you:

Run diskwarrior 5 file vault