Here's a step-by-step guide to help you reset MFA manually, whether you've lost access to your phone or you have purchased a new phone or want to add another phone.
1, Go to portal.office.com
2. In the bottom left corner, click your profile button (either a photo or initials)
3. Click View Account
4. Click Update info in the Security info box
5. Optional: Delete previous Microsoft authenticator push multifactor (MFA) device, if not in use anymore
6. Select Add sign-in method > choose authenticator app as a method > click Add
7. Follow the instructions on the screen to setup MFA Setup MFA with Microsoft Authenticator