I cannot log in a VNC session after the screen locks: "Authentification error". Why?
Solution 1:
I just encountered this error on a fresh install of Ubuntu 20.04, using TigerVNC. It seems to be an old error: https://bugzilla.redhat.com/show_bug.cgi?id=960149
A workaround is to SSH into the machine and unlock the session: loginctl unlock-session. I'd love to see a real fix for this.