Forbidden You don't have permission to access this resource

Hello,

I installed a self-hosted gitlab (with rpm - Omnibus GitLab) on ubuntu 20.04. I configured HTTPS with wildcard-certificate and the gitlab is running. But for example: if I try to change some settings in ‘Sign-up restrictions’ or ’ Sign-up restrictions’ I get this error. Forbidden You don’t have permission to access this resource. Do you have and idea what is wrong there or in which logfile I can find a hint?

Kind regards,
Korinna