There are several possible reasons for this.
Digitization error
When digitizing your email address on your profile card, it may have not been properly digitized.
Please check your profile card in the app and edit if necessary.
Instructions on how to do this can be found here.
Your email address is already registered
You wont receive a verification email if you already have an Eight account set up with your registered email address.
Check here to check if you already have an account.
Email settings
Please check your junk folder to see if the email hasn't been marked as spam.
The verification email will be sent from "notification@8card.net".
Please add the domain "@8card.net" if you can set filtering options by domain.
You've reached the send limit
To ensure security, we've limited the number of times you can send the verification email.
If you've sent it several times, please try again in 24 hours.