The game failed to load . Error code 3.

The newest game patch broke several mods and custom content. This can happen as we get updates for the game. Players using mods and cc have to go through their mods folder to find what needs to be deleted or replaced. EA/Maxis aren't responsible for broken mods/cc. It's up to the creators to fix.

Disabling or turning off both mod/cc options isn't enough of a test.

To test this, move your mods folder to the desktop, clear your game cache and delete the localthumbcache.package from the Sims 4 folder to help with troubleshooting. Try playing the game again to test. If it loads okay, it may be that some of the mods/cc have become outdated.

How to Delete Cache Files
https://sims4.crinrict.com/en/2014/09/delete-cache-files/

A list of some of the broken/updated mods/cc
http://forums.thesims.com/en_US/discussion/941998/broken-updated-mods-seasons-june-2018-patch

How To Find Problem Mods and CC
http://simswiki.info/wiki.php?title=Game_Help:TS4_Finding_Problem_Custom_Content

Try the 50/50 method:

1. Move all the mods and cc out into a temporary folder on the desktop.
2. Move a few files back at a time. Load the game to make sure it loads and
everything is good.
3. Delete the delete the localthumbcache.package from the Sims 4 folder.
4. Repeat steps 1 - 3 till there is no more files to check.

** While your testing, don't save the game. If you find any problems, delete the mod or custom content file.