Do you by chance use Tmex More Rental or MizoreYuki's Colour Slider mod? If so you might remove them, they could cause that specific error. If one of these is the reason for your issue check for an update or remove them from your game.
I don't use any of those two mods. The problems are still present after the most recent update.
@SweeetCheez I've moved you into a post that covers the empty build mode issue. Please check the known causes on p. 1. If you don't have those, please test "vanilla": Drag the Mods folder to the desktop, delete the file called localthumbcache, open the game to test, and exit without saving. If that resolves your problem, a 50-50 can narrow down the cause. I'd love to know what else causes this, so if you find another cause please let me know!
I'm having the same issue and you said to delete the localthumbcache file, but my says onlinethumbnailcache file? do I delete that one or no because thats the only thing showing up.
@Doodlebug330006 If you haven't restarted the game, it won't have a new localthumbcache file. If you have, the file is in Documents > Electronic Arts > The Sims 4 and is a package file, not a folder.
Check the Solution post on p. 1 of this thread for known causes. If that post doesn't solve it for you, you'll need to do a 50-50 of your Mods folder. Instructions are in How to Use Mods and CC
