Now I have this problem, up until now its been working fine for me, but today suddenly when I used my MacBook Spotify app and then without closing it I opened also the Windows App on my other computer**bleep** went crazy... now I can't see some covers of new tracks I have added to my fav list (but this might be a separate problem) and on Windows App no matter which solution presented on the forums (reinstalling sound drivers, the Spotify application, removing the app data folder or clearing the host files) I have tried I still can't play the music (but my MacBook or iPhone apps are working fine)... This looks like a major issue that quite a lot of people are having and remains unfixed until now.
Looks like I will have to take the pain of making new playlists in Apple Music but at least it won't let me down =/