If choosing to do your first-time login via the Apple mobile app, on the Code Confirmation screen please do not navigate away while waiting for the verification code sent via SMS. Allow it to auto-populate on the app so you do not need to leave that screen. If you leave the screen we have had users be kicked out of the registration process.
One workaround would be to do your first-time login via a desktop or mobile browser (not the app) and then once the initial first-time login is complete you should be able to freely log in to the mobile app.
