Unable to open sims4: Game Data missing error

@southernxbarbie  Do you use a third-party antivirus?  If so, please disable it temporarily and clear the EA App's cache:

https://help.ea.com/en/help/faq/clear-cache-to-fix-problems-with-your-games/

Then repair the game (again): open My Collection, hover over the Sims 4 icon, click the three dots, and select Repair.

If that doesn't help, please uninstall Sims 4 again, clear the App's cache again, and restart your computer.  Create a new folder on the drive of your choice where you want Sims 4 to be installed.  Put that folder on the root level of the drive, for example C:\Games is fine, but C:\Program Files\Games is not.  Open the EA App and install Sims 4 into this folder.  If you do have a third-party antivirus, leave it disabled while the game is installing, and don't reenable it until you've tried to play at least once.