One of my users keeps getting disabled every couple of days. I didn’t find any info about it, we have 21 users, could it be that I have 20 as a limit somewhere? i read that the limit was 100 so that shouldn’t be the issue.
they had no TOTP configured, so I instructed them to set it up
this user is (apparently) not doing anything different than the rest.
No. With more then 500 users you get a nice message on your login page and the push notification is disabled. Nextcloud fair use policy According to the source code, there could maybe also be 1000 users.
Does your user use a Nextcloud client (Windows, Linux, macOS, Android, iOS)? Perhaps they are repeatedly trying to log in with the wrong password. Can he perhaps reinstall the application?