Listed below are several reason why you may not receive your license key:
Filling in an incorrect E-mail address - the robot will send the message to this wrong mailbox and you won't receive it!
Your mailbox is full - the registration message can't be stored in your mailbox and you won't receive it!
You or your Internet provider use a so called AntiSpam program and it blocks the registration mail as a spam.
Please ensure that emails from Avast's addresses are authorized to enter your mailbox.