I loaded Origin today and was forced to move across to the EA app like everyone else here. I also go the failure to launch error that everyone has had and trawled through these comments to try and fix it. I somehow, miraculously have managed to do so, and thought I'd consolidate my steps here in case it can help anyone. Some steps are not fixes rather future proofing yourself from any of the horrible missing add-ons or other nonsense some people are experiencing.
So to save stuff:
- save a copy of your saves, tray and mods folders to your PC desktop away from the electronic arts folder
- take screenshots of your game and add-ons within the EA app so you have proof of what you owned before EA became completely ridculous. Scroll through to show all expansions, GP, SP and kits that show as 'in library'
Fixes that worked for me:
- cleared EA app cache - following the EA app specific steps here https://help.ea.com/en/help/faq/clear-cache-to-fix-problems-with-your-games/#ea-app
- repaired my game in the EA app (click manage on Sims 4, then repair, wait for it to cycle through)
- Right click on your existing sims 4 shortcut on your desktop, click properties, navigate to the compatibility tab, and ensure that 'run this programme as an administrator' is unchecked
- a second step here for me, as it didn't remove the admin icon from the sims 4 shortcut, so I just deleted the shortcut from my desktop.
The game then launched for me and the error code didn't appear. So I'll go and play and hope it doesn't crash but for now that has fixed the launch issues. I play with loads of mods too and didn't remove my mods folder, saves or anything to make this work.
I don't know which step specifically worked or it was a combination of all of it but I didn't have to uninstall the actual game at any point to get it to work. Maybe that's just how it worked for me but I hope this helps even one person...