Try a different email address (different domain) many ISPs do run anti-spam on their email servers and automatically delete and don't tell the user or send it to the junk/spam mail folder.
Try a free webmail account, Yahoo or gmail, have worked to resolve this apparent non-receipt of the email.
- You could also try the SSL Registration Page:
https://secure.avast.com/scripts/register.php?lang=ENG. Select the
My registration key has expired, I need a new one option and complete the form. Though I doubt this would make any difference if you use the same email address as it sounds like blocking rather than it not being sent.