I keep home directories on a separate /home partition. When I reinstall Ubuntu (generally Ubuntu-Mate), I format the root partition but keep /home and create user accounts in the same order with the same user names and passwords. When upgrading to Ubuntu 16 years ago, this worked seamlessly; old home directories decrypted just fine.
Now I just reinstalled up to Ubuntu 20.04.2. I checked around and it looked like everything should work the same as last time. I recreated the same user account with the same username and password but it won't unencrypt the old home directory. I can log in from the terminal to check things out but the graphical login just takes my password then kicks me back out.
Did something change in Ubuntu 20 that's causing the problem? Where can I look to track down the problem? Or was there something necessary to decrypt the drives that I blasted when I reinstalled and formatted the root partition?
