User signup is token based and can only be reached by clicking on the confirmation link in the confirmation email. The Confirmation email comes from firstname.lastname@example.org. To ensure you will receive the confirmation email add email@example.com to your address book.
It is also necessary to make sure our domains and IPs are whitelisted in your environment.
For whitelisting, please refer to this article:
If the confirmation email was not received, request a new confirmation email with a fresh token here: https://training.knowbe4.com/users/confirmation/new