This seems to be an emerging issue for Mac users since the June patch – the Sims 4 will not close properly when exiting out of the game. The game will appear to close but will still be running in the background. Using Force Quit does nothing and using Activity Monitor to quit processes doesn’t work either.
If you are suffering from this issue PLEASE post in this thread. The more info obtained the more likely we can come up with a fix.
Thanks 🙂
Bluebellflora 