Two users can’t be logged in simultaneously

I’m having an issue where two users can’t be logged in at the same time .
If one user lets their account lock when another user goes to login the screen will turn black then go back to the list of users login screen . This is similar to users not being able to login at all .
The only fix is to 1 restart machine or 2 have the other user logout .
I’ve tried downgrading the kernel but it that didn’t help .
I’m currently running 5.15.55-1.
I’ve read it could be caused by nvidia drivers ?
I’m fairly new to Linux in general so I’ll be as helpful as I can .
Thank you .

of course more than one user can use the system at a time
but also of course not at the same display - at the same physical terminal
but I may be misunderstanding something important here

A search using my favorite search engine

Let me try an clarify,
User 1 has documents and browser open doesn’t want to close everything so user 1 selects lock account ( suspends account) so user 2 can login .
When user 2 goes to log in that’s when the login loop starts .
Only way for user2 to login is to 1) reboot machine or 2) have user1 logout completely .

Can’t help, because i have xfce in a system with 2 separate graphic-cards and 2 screens for 2 separate users (+key+mouse). This does work with nouveau-driver