Sign in does not work


I have just upgraded Gitlab CE to the newest version and moved to another server.
The settings on the new server are the same as the old one except the host name is different.
We are using SSO authentication via SAML and also allow user to login via original built-in Gitlab password.

However, after transfer to the new server the SSO login succeeds while the login via built-in Gitlab password fails. I am not able to reset even my Gitlab password, because an error message is shown. it says password reset is not allowed: “Password authentication is unavailable.”

I am also not able to set or reset my built-in Gitlab password after successfully login in via SSO. Cannot find the menu for that.

In admin area I have set the following setting on, but it does not help: “Password authentication enabled for web interface” & “Password authentication enabled for Git over HTTP(S)”.

Two factor authentication is not set.

So, how can I enable the built-in Gitlab authentication and reset my password?
Why is it so difficult to enable such function? Is it not recommended to use built-in credentials?

Kind regards