The following are answers to questions that you may have when using a service that uses MFA authentication.
If you are having difficulties logging into a service that uses MFA for authentication, try logging into the MFA portal first. You will be able to use a backup method to get in (either text/phone call or answering your security questions) and then you can change your MFA settings if needed. Once you are able to successfully login to the MFA portal, then try to login to the service that uses MFA authentication again. Note that if you immediately log into the service after successfully logging into the MFA site, there is a short window of time where you will only be prompted for username/password and not your MFA authentication (phone call, text or Mobile app).
There are many more FAQ items in this document that may help you as well so be sure to see if your question is answered here first.
You are prompted for a PIN for all authentications except when you are using the Mobile App option and have enabled it to use your fingerprint. In this case, you had to enter your PIN when you set it up to accept your fingerprint, but after that you will not be prompted for your PIN while using your fingerprint.
There is a small window of time (a few minutes) where you are not prompted for your multi-factor authentication if you log back into the service. This window of time allows you to log back into the service and it will only prompt you for your username/password and not use your MFA authentication (phone call, text or Mobile app).
If you are using either the Text Message or Mobile App method, the backup phone number is not displayed on the MFA "Change Phone" screen. To change/add a backup phone number when you are using the Text Message or Mobile App methods, you need to login to the MFA portal where you will get an opportunity to use a backup method including answering your security questions. Once you are logged into the MFA portal, first you will need to change your method to Phone Call and then when you go to the option to change your phone number, you will now see the option for a backup phone number. After you have set a backup phone number, you can then change the method back to Text Message or Mobile App. The backup phone number will then be listed as an option if you fail to authenticate using Text Message or Mobile App even though you can't see it on the "Change Phone" page:
Note that the backup phone number is only called during authentication if you are using the Phone Call method and you failed to answer your primary phone. You will not get a phone call to your backup number if you are using the Text Method or Mobile App. For those methods, even though you can't see it on the "Change Phone" screen - the backup phone is used to verify your account after authentication has failed when you are accessing the MFA portal. See the FAQ item next about when the MFA backup method is used for more information.
Follow the changing or adding a phone number steps in the MFA document.
If you are using the phone call method and you do not answer the primary phone number or it goes to voice mail, then it will call the phone number you have defined as your backup phone number after it did not reach you on your primary phone number.
If you are attempting to login to a service that uses MFA using the Text Message or Mobile App methods and you don't respond or incorrectly authenticate (enter wrong text passcode or PIN) it will give you the "Incorrect user name or password" error only and will not use your backup method. If you don't have access to your text message or mobile app, you will need to go to the MFA portal in order to be prompted to verify your account by using one of the backup methods (text/call or answer security questions). After you have verified your account by successfully using one of the backup methods, you can then make changes to your MFA settings and then you can log into the service that uses MFA authentication. See the FAQ item about adding a backup phone number when using text or mobile app method.
If you forgot your PIN, follow the changing your PIN steps in the MFA document. You may need to wait till it times out after entering your username/password, then answer your security questions to initially gain access to the MFA portal.
If you don't have access to your text message or mobile app, you will need to log into the MFA portal. It will prompt you to select which backup method you'd like to use. You may then choose to receive phone/text on either your primary or backup phone number or answer your security questions to proceed. Once logged into the MFA, you can choose to make changes to your MFA settings. See the FAQ item about adding a backup phone number when using text or mobile app method.