Office 365 - I can't sign in with MFA (New phone or Phone number)

This article explains how to change your MFA registration to update your phone number or re-register the Authenticator app.

Steps

If you recently changed to a new mobile phone or changed your phone number, you may experience issues logging into your UWS Office 365 account. Follow the steps below to update your MFA registration and get back into your account.

Re-register Authenticator App to a New Device

New Phone, Same Number

Go to aka.ms/mfasetup
Log in with your account
Click on 'Having trouble? Sign in another way'
Select a different MFA option to receive a code
Once signed in, click Delete to remove the current app
Click 'Add', select 'Authenticator App' and then 'Add'
Follow the instructions to set up the app on your new phone
This will allow you to use the app now on your new device to get past the MFA authentication.

New Phone, New Number

If you got a new phone and a new phone number and do not have access to your old device and phone number, you will need to submit a ticket and request the IT Service Desk to reset your MFA registration.

If you have access to your old number and device, please follow the steps above to re-register the app. To update your phone number, follow the instructions below.

Update Phone number for MFA (Have access to old device and/or phone number)

Go to aka.ms/mfasetup
Log in with your account
Click on 'Having trouble? Sign in another way'
Select a different MFA option to receive a code (if setup, select Approve with Authenticator App - This is not phone number specific, but rather device specific)
Once signed in, click Delete the current phone number
Click 'Add', select 'Alternate Phone' and then 'Add'
Follow the instructions to add a new number

If you have any issues updating the registration yourself, please submit a ticket. The IT Service Desk can remove your current registration. The next time you sign in, you will be prompted to register again. Note, the IT Service Desk cannot update your phone number, only reset your registration entirely.