DENON AVR X-1000 "User allready exists" (Benutzer ist bereits vorhanden)

[RILHADKOA]

Spotify premium on my DENON AVR X-1000 worked fine untill today. Suddenly it wanted that I have to login again. But it doesn't accept my correct device-username and password. I allready changed my password but it didn't changed anything. I allways get the errormessage "User allready exists" (Benutzer ist bereits vorhanden).

I did nothing unusual. I did not registered another device. On my smartphone and computer everything works fine.