Supported authentication challenges

You should note that only the authentication challenges that are available in a user profile can be presented. For example, you might select Phone call and Email confirmation code in the authentication profile, but these challenges are only valid if users have both a phone number and email address stored for their accounts.

If users only have a phone number and not an email address stored, they will receive a phone call to complete the authentication process rather than be prompted to select an authentication option. If users have both a phone number and an email address stored, they will be prompted to select which form of authentication to use.