Sims 3 Supernatural expansion pack for PC/MAC issues. Downloaded from Origin.

I have just purchased, downloaded, and installed (but probably not successfully) the Sims 3 Supernatural expansion pack for PC/MAC (I own a Macintosh). I have downloaded the game from Origin. It was my first purchase on Origin, and I'm having a lot of trouble with the Sims games now.
I own the Sims 3, and the Sims 3 Late Night expansion pack. Both, I have bought/installed as disks, and besides the occasional 'exception raised error' that started appearing after I started playing on Late Night, I've had no problems.
Anyway, I've just purchased the Supernatural expansion pack and downloaded it. I've installed it, too, and everything went okay until I clicked on the Sims 3 Supernatural in Applications, trying to play it. The launcher came up, as it should, but when I pressed the 'play' icon, the game did not load. The big Sims diamond appeared in the middle of my screen after I pressed 'play', but soon after, it disappeared, along with the Supernatural icon in the dock. I've tried again and again, and I get the same result every single time. I've put in the Sims 3 disk and the Sims 3 Late Night disk, but I still am unable to play Supernatural, or any of the other Sims 3 games I had bought before (as disks).
I'd really like to know what's going on and what I can do to play my Sims games again. Thank you in advance for any help.