Unable to log in or create new users

Hi!
I am running gym CE on kali for months now and it worked fine until yesterday.
Since yesterday I am unable to log in on the web interface.
“Login Failed. Invalid password or username.”
I tried to change the password on the console

sudo runuser -u _gvm -- gvmd --user=xxxxx --new-password=yyyyy

ran without error, but did not change anything.
creation of a new user:

sudo runuser -u _gvm -- gvmd --create-user=zzzzz -new-password=yyyyy
Failed to create user: Invalid characters in user name

Even “admin” is not accepted.

gvm-check-setup runs without errors

--rebuild as well

What now?

Should be a duplicate of Can't create GVM user, throws an error "Failed to create user: Invalid characters in user name"