Our data indicates the vast majority of users are playing Thumper without a hitch, but we're aware of some tech issues preventing some players from running the game (and we've seen your support forum posts). We've been sidelined by personal matters and injuries, but we're making a maintenance update a priority now and hope to have it out within the next month or so.
Thanks for your patience.
That said, if you recently purchased the game and are having problems running it, please don't hesitate to take advantage of Steam's refund policy if you'd prefer not to wait. The last thing we want is for you to get stuck with a game you can't play.