My Steinbery login appears to be corrupt

I am trying to purchase the upgrade from Cubase 11 to 12. However, when I get to verifying my details, the email address shown is an old one. When I try and correct this, it says the new email has already been used and won’t let me continue. I am concerned that, if I let it use the old email, any correspondence will be sent to the defunct email.

Also, when I have tried to create a support query, the final stage goes back to the Steinberg home page instead of the one where I input the query!
Any help would be appreciated, as I am running out of time on the upgrade offer!