I decided to make this a new topic because it has nothing to do with my initial error anymore.
I have recovered my sunrise cabinet from the KUKA Recovery USB stick. I chose "recover from hidden partition" because "recover from usb stick" ended in a "nothing to do here" boot message.
Now when I boot my sunrise cabinet, startKRC runs as expected but smartHMI does not open and when I try to open it manually from desktop, it turns out that the folder C:\KRC\SmartHMI does not exist anymore. Any ideas how I get the software back?