And then you proceed abou the upgrade, again, you will need to enter a billing email as showed below. This is your billing email from which you will receive your order notifications like payment, account renewal and so on. To renew manually, or stop automatical renew, to refund, all through this email, read more details please.
So please remember to login through the first email, the DWG FastView account email, not the billing email.
By the way, another question frequently asked, if you register or login by social networks such as facebook or google, you can't login on our Windows client whose social login feature is not added yet, you have to add a login email on the website by social login first.