No client connection via subdomain

Hello, I have a shared webspace with cpanel, mysql and nextcloud 12.0.5.
When I go over the domain (for example,, everything works fine. The connection via CalDAV, CardDAV, iOS and Windows runs without problems.

But if I put the same installation on a subdomain (for example, I can access the web interface via the subdomain, but I can not connect to other services like the windows client.

ssl certificates are installed and working for the domain as well as the subdomain.

I took a screenshot of the error of the windows client.
Maybe someone can see something with it.

when I go over the browser on the status.php I get the following message:


since days I sit at it, but unfortunately find no solution.
I hope someone can find the problem here.