Onlyoffice android broken with Seafile 7.1

Hello,

after upgrading from my Seafile server from Seafile 6.3 to Seafile 7.1, unfortunately the OnlyOffice Android app no longer works.
Whenever I switch to the Clouds tab I get the error message “Connection error. Try again.”

There is no error in the Seafile / nginx logs.
Also none in the OnlyOffice logs.
Other WebDAV applications work with my Seafile server without problems.