The Ussun website still works, but I don't know if they're in the business anymore. There are three emails on the Contact Us page created by them. You will have to use those to reach the developers because it's the only way.
I think that what you see on the page is actually the remains of their website that is somehow still working after all these years. I am really sorry for the trouble, but the developers are the only ones that can provide with information regarding the status of your serial number.