PROBLEM SOLVED!
In my case this helped out:
Uninstall Scaler 3 an d reboot.
After Reboot: (Re)install Scaler 3 (Dont Start Scaler or your Daw!)
Now Reboot again. - Then Start Cubase with an empty Projekt and load Scaler 3 as an instrument.
In my case Scaler loaded properly and it works since then.