I have a 2014 MacBook air (1.5 GHZ i5, 4GB RAM, 128GB SSD) which was able to run Sims 3 just fine on El Capitan. I update to macOS Sierra and now my Sims 3 and Sims University add-on refuse to run. The initial start screen with the gem and the 3 show up, but it never boots past that. Just stays on that screen no matter how long I wait.
Have you moved out your Documents > Electronic Arts > Sims 3 folder onto your desktop and tried loading the game?
Have you tried uninstalling and reinstalling the game?
