2019 Sims 4 CAS Sims not saving to Library!

@bernicenava

You have probably outdated UIC mod
Move the mods folder to the desktop.
Delete localthumbcache.package file in the game folder
Fix the game in Origin.
Origin/Library -right click on TS4 - option "Repair game"
You have to wait until Origin will fix all packs, not only the base game.
Turn on the game to create a new, empty mods folder and check if a game is working now without mods and CC.
Check if there are new updated versions of the mods and CC you are using.
Then copy from desktop your mods and CC and paste it in the new mods folder. First, paste script mods one by one every time checking if the game is OK. Do the same with CC but if you have a lot of this, try the 50/50 method. ( divide your CC into smaller batches for example 50 pieces in one subfolder and check these subfolders one by one)
You need to find a culprit and either remove it or replace it with an updated version

I don't work for EA