Just to get some basics, your Spotify account is registered from Germany, and you are currently in Germany while using the Spotify service?
You are not currently traveling outside of the Country you registered your Spotify account in?
Hum you might try removing the Spotify linked account on the PS4? And see if trying to link up again on the PS4 helps. I am going to go ahead and move this post over to Help - Other https://community.spotify.com/t5/Help-Other-Partners-Windows/bd-p/002 maybe some other PS4 users might have some suggestions?
Do you have any issues logging into the Spotify service through any other devices with your Spotify log in information?
I found this webpage but it is the U.S. support page from SONY about how to unlink Spotify accounts here: https://support.us.playstation.com/articles/en_US/KC_Article/PlayStation-Music-featuring-Spotify/ Scroll down to the unlink instructions on the page.
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