I've had the exact same problem since about Saturday. Just like you said it won't let me play stuff from artists I haven't listened too before. I tried everything and nothing seems to work. Btw Spotify on my phone works fine, Spotify downloaded on my computer is having this issue. Let me know if any of you guys get an answer.
I've also been experiencing this problem. The only solution I have found on multiple threads is to uninstall and reinstall Spotify, but this seems to be a temporary fix rather than a permanent one. I really hope the devs can get on top of this problem, because it's super obnoxious to deal with and almost makes me want to go back to Soundcloud.