Bambu Studio no Upgrade possible: "Bambu Studio is running"

A Friend of mine with his Bambu Studio: when he tryed to upgrade, the message is “Studio is running”. When tryed Studio de-installing, same message. Even when tryed the studio.exe in the windows10-path to delete, same message. Windows Task Manager tells, Studio is activ in the background.
Windows down an up. WLAN down an up. Studio started and exit. No way. Any Ideas? Thanks a Lot.

Roscano