Cant activate Cubase 9 Artist Edu

Hello - I bought and installed Cubase 9 Artist Educational edition. But it kept crashing. So (before I had registered) I tried uninstalling and reinstalling. Then when I re-entered the Activation Code I got an error message ‘This code has already been used - contact your retailer’. I just tried phoning them, but cant get through. Doas anyone know what the solution is, please? If I finally get through to the retailer will they be able to give me a new licence, or can someone at Steinberg help?

Thanks for all info and help