When things are going smoothly, you can expect to get a 'StartNextChallenge' or 'LoginSuccess' response, however the system may (at any time) return a new Mfa Package which may add, remove or change challenges. Failure cases typically result in an 'Undefined' error message when things are misconfigured and a "LoginFailure' message when incorrect answers have terminated the session (which may have been sent in previous calls to this API).