I just made it work suddenly. The solution was to play around with the languages. That means I logged out from Spotify. Logged in again. Had some problems with the log in and had to change the language to US English and to enter my adress, with postal code and street. Then I could log into spotify again. After that I chose Spotify as my standard player, but it did not work. So I changed back the language into German and worked. Hope I could help someone. Cheers.