Re: Sims 4 won't open after Dec 2020 skin tone update

@rant286  It's probably your mods.  Please move your entire Mods folder to the desktop, delete localthumbcache.package, and see whether the game opens.  If it does, you can add back your mods in batches, testing each time; any batch that prevents the game from opening needs to be split and tested again until you find the problem file(s).

It may be quicker to replace your mods with new ones, at least for the mods that have been updated or otherwise confirmed to work with the newest patch.