sims 4 wont launch after update and installing expansion pack

@lushifii  This is typically a OneDrive error: OneDrive is in the process of syncing the folder and won't let you move it until it's finished.

First, before you do anything else, make a backup of the entire Sims 4 folder.  Right-click it and select Copy, then right-click and paste where you're storing the backup.  Ideally, you'd use an external drive or USB stick, but if you don't have one handy, put the copy in Downloads.

Next, pause OneDrive syncing and cancel the current sync:

https://support.microsoft.com/en-us/office/how-to-cancel-or-stop-sync-in-onedrive-4885c27e-3d89-4d69-be75-2646c71367d3

It's best to then stop OneDrive from syncing Documents entirely:

https://support.microsoft.com/en-us/office/choose-which-onedrive-folders-to-sync-to-your-computer-98b8b011-8b94-419b-aa95-a14ff2415e85

This will likely remove the local (on your computer) copy of the Sims 4 folder as well as anything else in Documents.  You can still download the files from OneDrive, either through the app on your computer or through the website.  But you also have the backup of the Sims 4 folder, so you don't have to worry about that at least.

Finally, go ahead and test the game as discussed earlier.