Cubase upgrade first install no longer supported

I purchased an upgrade to Cubase SX some years ago now but was unable to install and register it as my DAW, at the time. became unservicable.

I finaly got round to making a new build this week only to find that My product key would not allow me to use this software, and when I visited the Stienberg website it informed me it was no longer supported.

This is expensive software and I don’t see why I should have to pay the full price by starting again.

I have my dongle and I have a valid activation code (un registered.

Could someone at Steinberg please advise as the webpage will not allow me to register without an account which I cannot create as I do not have a legible Cubase product version.