Why won't the sims 3 open on my Mac?

So I have the Sims 3 with Late Night. I wanted to play it one day and I did, but then the next day, I tried to open it up, but it wouldn't even go to the game launcher! It said there was a download available but it didn't download anything. I clicked on The Late night button and it appeared in my doc, but then It just went away. So I also tried opening the regular sims 3 launcher and the same thing happened. Does anyone know how I can fix it?