I bought Scrivener back in 2014 and kept my receipt. I had to reinstall windows and when I did, I lost Scrivener. So I downloaded it again, located my receipt which I still have, and then tried to register it again. It’s the same computer as when I bought it.
I entered my name and serial number as it is on the receipt but it’s telling me that the serial number is invalid.
Your current serial number should work. If you’re copy/pasting it from an email, make sure that you’re not inadvertently including an extra space at the start or end of the number when you paste it in - apparently that’s a common mistake.