The email address you are using appears to already be linked to a SecureIdentity account.
This may be the case if you share the email account with another person. In order to create your SecureIdentity, you will need to use an email address that is unique to you. So you might need to create your own email address.
Another reason you may have clicked on a registration journey and the automated system is advising you that your email is already registered so you will need to Sign-in rather than Register.
If you clicked on Repair my Identity, this is a re registration process and you will need a different email to the original one you have initially registered with.