Cryptomator on android: webdav on euserv: no files on tresor shown



I’m trying to use cryptomator to access my cryptomator tresor I uploaded to my euserv driver.
In the android app I can setup the webdav connection and browse to the masterkey file.
The list entry in the main screen is created. I also can open the tresor using the password.
But then the app says that there are no files in the tresor.
This happens on my smartphone as well as on my tablet.

When I browse the folder with Dolphin on Linux I see the (encrypted) files, accessing the directory with cryptomator to decrypt the files on my linux machine also works fine.

Does someone have a hint what I may do wrong?