There are a few reasons why this might be the case. First, verify what email address you have chosen for the Doman Control Validation email (please note: this is different from the contact information provided during the generation process). If you need to change your DCV email, you can use any email on the Whois registration for that domain or one of the five following pre-approved alias email:
Admin@domain.com
Administrator@domain.com
Hostmaster@domain.com
Postmaster@domain.com
Webmaster@domain.com
Also, make sure to check the Spam or Junk Mail folder of your email provider.