Collabora Error reading of document failed

I installed today the Hyper-V VM from tech&me with Collabora. Everything works fine, only Collabora won’t work. If I click on the example.odt or on a new created odt-file Collabora starts (menu is visible) and the circle with “initialize” rotates. But then I get the error message that Collabora can’t read the document from storage (in German is the exact message: "Lesen des Dokuments vom Speicher fehlgeschlagen. Bitte kontaktieren Sie den Administrator Ihres Speicherservers (cloud.meinedomain.de).
I created the VM a second time, but same error occurs.
What can I do to solve the problem?
Thank you!