Hello,
Apply a Windows theme instead-
Go to Start > Settings > Personalization > Themes.
Select the Windows Bloom (light/Dark) theme you would like to apply.
Make sure to click Save.
If you are still having issues and the suggestions recommended by AI and ApexNav did not help,
Open a CMD (Admin) window and run the sfc/scannow command.
Once completed, restart your computer and apply the Windows default theme.