This problem just occured early this morning. I clicked on an artist I've been listening to a lot recently without any problems, and it says I don't have any playable songs. Weird. So I clicked on "Songs" where all of my music is downloaded and tried to listen that way, the songs was available and able to play. I also searched the artist in the search bar and was also able to listen to their music. The same problem with other artists. Actually it's more of a problem with lesser known artists, if that's important. I researched that the issue could be the artist music is no longer available in my country or that there are issues in the agreement between spotify and the artist, but that can't be the problem because I'm still able to listen to their music. I went to settings to show unplayable songs like the error told me but it didn't help with anything. I restarted my phone and nothing changed. I also deleted the app and downloaded it again, no change. Please help! It's not really a big issue, but the app is less convenient now and takes longer to navigate which is annoying.
[Problem solved! Just needed to update the app. Silly me]