Bug/Issue Unable to Launch Game

I've been trying for the last couple of days to launch my game through Steam, but each time is says 'Preparing to launch', tells me I'm in-game (I'm not), then switches back to just online. I've tried everything in the list of suggestions on the 'how to fix your game' sticky thread on the steam forums and several suggestions throughout the forums but nothing has worked! I'm hoping someone here knows something that might help?

Also, frustratingly, no error logs are coming up in %appdata% so I can't provide any of those for help.