Re: Sims 3 doesn't work on EA App (how surprising)

@Csabuszkah  The first step in troubleshooting would be to move the Sims 3 user folder out of Documents > Electronic Arts and onto your desktop.  If it copies instead of moving, or you get an error when trying to move it, stop here and let me know.  Otherwise, launch the game, which will create a new folder, and try to start a new save.

If it works, the problem is something in the old folder.  You can try copying over one of your old saves, but nothing else; please use a save that takes place in one of the built-in worlds, e.g. Sunset Valley or Bridgeport, rather than a Store or custom world.  If that works too, and you have saves that take place in a Store world, try installing just that world and loading a save that uses it; you can also do this if all your saves require a world that needs to be installed separately.  In either case, since you're copying over the save rather than moving it, you don't need to worry about missing content—the original save will be intact in the old folder.

If you still get the same error with a new save in the new Sims 3 folder, restart your computer and disable your antivirus, then test again.  As long as you don't open anything other than Sims 3 and the EA App, your computer should be safe.  If you only use Windows Defender, disable Controlled Folder Access instead.  In either case, if this helps, you can set exceptions for Sims 3 (TS3.exe) and the EA App and test again.