I have McAfee Antivirus and I've never gotten a notification that it blocked or quarantined TS4.
I looked at the Reliability Monitor, but it didn't show any errors occurring at the time this un-launching episode began.
@aucqz16dqw4c Just in case, I did mention restarting before testing offline mode, but are you restarting your computer every time this happens? If not, that should always be the first troubleshooting step. As simple as it is, it can fix a lot of weird errors.
The fact that the Reliability Monitor shows no errors makes it likely that something is blocking Sims 4 from running, and perhaps blocking its access to the user folder. OneDrive would be the first suspect after your antivirus: perhaps OneDrive is trying to sync and taking its time. If you don't want to unlink it, you could try blocking Documents from automatically syncing:
You may need to cancel syncing or stop the current sync before changing the settings:
Before you mess with OneDrive, make a backup copy of anything critical inside Documents, including your Sims 4 folder. When you set OneDrive to no longer sync, it can often remove the local copies of everything, leaving only the cloud copies. It's easy enough to download the files again, but even better to have a spare copy, and that prevents any data loss from the sync process being interrupted.
If you don't want to mess with OneDrive at all, you can set up a new admin Windows account on your computer. Make it a local account: no signing into Microsoft means no link to OneDrive. You don't need to permanently switch over; the point is to test and see if you can get around the error in the moment.
