I use diskutil to unlock file vault.
I use "diskutil cs list" to get the logical drive and then "diskutil cs decryptLV ${lvUUID} -passphrase $password" where lvUUID is the UUID of the logic drive.
@sam.hummerstone, I ran into this problem a lot back with Mavericks. Typically, but not always, a simple reboot of the client machine was all it took to get things back up an running. When you are prompted for the password or recovery key, are you entering a known FV2 password, or are you trying to use the recovery key? Make sure you are using a password instead of a questionable key.
Also, as you may or may not know, if you don't have a config profile to redirect the recovery key, issuing a fdesetup changerecovery will not update the key in the JSS. @roiegat's suggestion will do a full decrypt, so you'd have to re-encrypt when it finishes. When I had machines doing this I usually wound up doing the following:
- Reboot client computer
- Use a known FV2 password to add the JSS management account to FV2, if it's not already there
- Use a JSS policy to re-issue the individual key
- Verify new key is accurate:
sudo fdesetup validaterecovery
- Remove the management account from FV2
If all that failed, I was forced to decrypt the volume using an institutional key and then re-encrypt.