Since the recent patch the game is resetting my display settings on launch and reverting the game to full screen mode. I play on windowed with a custom resolution and it is being reset when launching the game after a PC restart.
What security software are you using ? This is often caused by ransomware protection blocking user files so make sure to add Sims 4 as exceptions.
If this doesn't help, try deleting the options(.ini) file and let the game create a new one. You'll need to reset everything but hopefully it works afterwards.
mine has been doing the same as well. I just play on fullscreen windowed. And every time I restart my pc it reverts to fullscreen which causes my other two monitors to go black screen while Sims 4 loads up.
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