Issue with mysteinberg account!

Hello, i need some assistance in order to download again the cubase 8 mac installer. I bought the Cubase 5 years ago, then i upgraded to 8 pro via web. The mail i used to register my products is no longer available, because a change of server and name of the company. I lost my password of that user, and i requested change of password, without noticing the mail it wasn´t working anymore, so, i´m in limbo right now. I can´t register my product, because is “already registered” to a mail account i don´t have access anymore. My Backup HD went wrong last week and i lost everything, including the Cubase 8 full Installer. So, what can i do in thais case to get my installer back, and the access to my account in order to eventually keep upgrading my system?

Thanks for the consideration. Best Regards.
Nicolás Arce