There was an issue that made it impossible for some players to get the single-player achievements that I'm fixing.
The issue was that the client only reported its single-player scores to the server if the scores were better than the previously earned score. I previously stated that players just needed to win a level again to get the achievements, but players who already had very good scores couldn't really better their scores to get the achievements.
Now, I'm reversing what I previously said. All single-player achievements will just automatically show up on your profile.
The server is working on giving them out to everyone now, one player at a time. It may be a few hours before it gets through everyone.
