Your multi-factor authentication (MFA) using the Microsoft Authenticator app is linked to a specific device.
1. If you still have your old device and are moving to a new device:
Set up MFA on your new device before resetting your old device. This can be done by following the same steps for setting up MFA by going to your Microsoft security info page and going through the setup. Once you have set up Microsoft Authenticator on the new device, you can remove the old phone from your account on the same security info page. Now the authentication prompt will appear on your new phone.
2. If you cannot use your old device:
If you have lost or broken your device, reach out to the helpdesk by calling 416-415-5000 ext. 4357.
For more information, see the MFA Frequently Asked Questions.