Mac App Acces Denied

I have installed Nextcloud 15 behind a Sophos WAF. For the Installation I use this Guide

All is running fine and I can login via Web to the Cloud. But if I try to connect with my Mac Nextcloud App and I enter my login credentials I get the following Error Message:

Access denied.
Status-Token did not match.

When I login with my iOS App i must enable “go to the old Authentication method” and login via mobile App is working.
But I can not set this settings in the Mac App.

2Factor Auth is not enabled.

Any idea what is the Problem?