So yesterday I clicked 'Play your mix' on last.fm website as i do everyday but this time it didn't open spotify and showed me an error message saying 'You’ll need Spotify to play this track!'. I do have my spotify ready and waiting ... Thanks in advance for every solution.
Spotify have changed the library we use for playback, we're expecting them to have this fixed later today.
Small update if you missed my comment below: Unfortunately we're still waiting on Spotify's developers to restore the service we rely on for playback. We're also working on an alternative solution using their api, in case they don't follow through; so with a bit of luck we should be back up an running again soon. For now though, only Youtube playback will work, you can change this in your playback settings. Sorry for the hassle in the meantime.