I'm experiencing the same issue as @lozzajanex2 and @Fabius_SimTube. My game launched perfectly fine until yesterday, and today TS4 and TS3 wont open because they are 'already running'. I used different methods for troubleshooting, but the only thing working is setting my computer date back to june 1. (I only jumped two days forward in time, non working.)
I also logged into my account on my gaming laptop and the game starts without issues.
same here! I don't know what to do, I feel like I've tried everything. I use Avast (can't uninstall or open the app for whatever reason).
@shutupjolie Try setting an exception in Avast for the entire Bin folder inside [install location]The Sims 4\Game.
