Login in Client not working

I have a problem with my freshly set up Nextcloud 11.0.2 Instance.
I created 2 Users in the Web Interface and with both users I can successfully login on the Web Interface. However, when I try to log in using the Desktop Client (Tried Linux Version 2.3.1 as well as Windows Version 2.3.1) I get the error message “Access forbidden by server…”.
In the logs I see when I try to login with a wrong username/password in the web interface but when I try to login with the client nothing is written to the Nextcloud log.
I tried to login with Username/Password as well as with a generated App Password.
My System Setup is:
CentOS 7
PHP Version 7.1.5
Followed the instructions from the Nextcloud Website to install it.
Thanks a lot for your help, if I shall post any other information please let me know.

Loesung: In meiner Apache Konfiguration fehlte der Abschnitt

Dav off