I honestly don't know what happened. I was deleting some script mods and joined to a message that said "The game failed to load. It is recommended that you relaunch the game." I did as it said but it still happened. I deleted a file named "localthumbcache.package" and joined to no sims including the one sim I had in my household.
I finally found out the problem, a mod I had downloaded had some virus and was messing up my game.
You could just move "The Sims 4" folder to your desktop or somewhere else and start the game. It will create a new "The Sims 4" folder. Then copy the saves and tray folders from the old "The Sims 4" folder to the new one. If that doesn't work, then try a game repair. Deleting the localthumbcache file is usually safe but you might have deleted a game file accidently so letting the game create the new folder will restore those files. If that doesn't work then you probably ought to repair the game and try again.
Hope this helps.
I finally found out the problem, a mod I had downloaded had some virus and was messing up my game.
