The only thing I'vce noticed different about my setup is my files are located in OneDrive. However, I've actually turned off OneDrive because it tends to mess up my system. I uninstalled it once and had to wipe and redo my Windows.
@tenoddcats If the location of your Documents directory is still inside OneDrive, you can change it without reinstalling Windows:
Sims 4 should place the user folder inside the default Documents folder, wherever that is.
If you don't want to mess with this account's settings, or changing the location of Documents doesn't help, it's worth setting up a new admin account on your PC to test. Make it a local account, as in, don't sign into Microsoft, and OneDrive won't be involved at all. You'll need to download your mods again, but not the game. If this works, that's useful information in that it points to an issue with your existing account rather than your computer overall.
