I'm dual booting Windows 10 and Ubuntu 16.04. My Ubuntu partition is encrypted, and I have a separate boot partition.
A Windows update wiped out GRUB, so I used boot-repair to reinstall it. I got a dialogue about decrypting a volume, but couldn't work out what it wanted me to do. Otherwise, it seemed to work OK.
The GRUB menu now appears, but when I try to decrypt it won't accept my password. However, if I boot with a live USB, I can decrypt the volume with
sudo cryptsetup luksOpen /dev/sda6 encrypted and the same password!
I've run out of ideas of what to try next. My guess would be either to run boot-repair again and do something about the decryption error, but I'm not sure what.
Sorry about the vague descriptions of errors - I don't have access to the PC at the moment. If there's some information that might be helpful I can fetch it tomorrow.