Can't validate sms code when Signup is disable on SMS connection

If you disable public signups for a connection then you’ll need to create the user from your own backend through the Management API (Auth0 Management API v2). I confess I may be missing something around the requirement for validating the phone number given that for an SMS connection if the end-user completes the login then the phone is validated implicitly so you may want to expand on your exact scenario.