Uninstall product key.
Install product key.
Verify product key activated.
Saving file or deleting file to/from desktop did not work until you manual refresh or hit the F5 key.
Click Start. Hold Shift & Control keys together, right click mouse above the ‘Shut down’, and select Exit Explorer. You will get blank desktop.
Go to Task Manager (Ctrl+Alt+Delete). Create new task in File menu and type Explorer and OK. See below.