Sims 3 says it is already running, but it is not?

Hey, so I've recently bought a 2015 Mac Air with Intel HD Graphics 6000 and everytime i try to play the game it says:
cannot start the process when the game is running. please quit the game and try again.

Its really annoying and I know I'm pretty late to this convo but I really don't know what to do, any comments will help! :blush: