Namespace is not valid

Hi all,

I am running a self-hosted CE version for GitLab version 13.11.2 on CentOS 7.

I (and other users) used to create some personal projects unter my “user name” as namespace (just the login name derived from LDAP) where I do have several git repositories, so this actually worked (also for other users) .

Just now I wanted to create another “personal” project but do receive the error message “The form contains the following error: * Namespace is not valid”. As I try to keep the instance up-to-date but do not create new projects every day/week I can not tell since that version this is no longer working.
Creating a project in a group does work as “always”, transferring this to my “user” namespace does also lead to an error message “Transfer failed, please contact an admin.”.

Is this expected behaviour?
Do I have to allow creation of in the personal namespace somewhere?
Searching this forum (and elsewhere) only led me to issues where the default creation protection was set to “no-one”, in my case this is “Developers + Maintainers”.

Thanks for any hints and pointers!

Best,
Markus