I have just bought crusader kings II on steam and when I click play it comes up with the CD-key which I need to launch the game. I have registered the game on here however when I click "Start CKII" on the new window which is brought up, absolutely nothing happens. The game does not launch whatsoever. What can I do? I don't want to have spent £30 on this game only to be unable to play it... I have limited technical knowledge by the way.