Your phone number could already be linked to an existing TSA account. A phone number can only be registered to one TSA account.
There are two possible reasons why your phone number may already be linked to an existing TSA account
You might have signed up for a TSA account that is registered with this mobile number before. If you have forgotten which email address you used to login previously, you can use the Forget Email function to retrieve the email address and login thereafter.
Your phone number was recycled. As phone number might be recycled by service providers, it is possible that your phone number previously registered a TSA account by someone else. This does not mean that you can access the previous owner’s account or vice versa. You can contact our support via the Contact Us function to help you with the signup process.