Many web messaging services, including GMail, identify the activation mail as Spam, and send it to your spam folder, instead of inbox.
If you are using GMail, follow these steps:
1. Open your Spam folder.
2. Search your spam for a mail from genymotion-activation@genymobile.com with subject "Welcome to Genymotion - User account activation".
If you still don't find the mail, make sure that:
- Your mailbox is not full.
- You spelled your email correctly when you registered.