How do you get Sims 3 via Steam, to start?

I've spent hours on this to no avail. When I click the new Sims 3 desktop icon that Steam installed, it gives me a popup saying I need to copy the activations key (already did, and entered them all at sims 3 store) and if I hit play, both that popup box and the one that is supposedly starting the game, just close, and that's it. Nothing.

Any ideas, anyone?