If you’ve already set a default method, just make sure it’s set correct after deleting the old method.
Finally, if you have’t set one already you can set the default sign-in method by clicking the link Set default sign-in method found just above the + Add method button.
When you’ve located it click the Delete link to remove it
Identify the old method linked to your previous device you can click the reversed caret ( ^ ) button to expand more details to help you identify the correct method.
You should see an additional Microsoft Authenticator method now listed alongside the previous methods.
Follow the prompts to set up the Microsoft Authenticator app on your mobile device including scanning the QR code and approving when prompted.
Make sure to select Authenticator app from the drop-down menu then click the Add button.
In the Security info page you should see existing authenticators and/or app passwords you may have set up previously.
Under the Security info section, click Update Info Set Up your MFA Options How to Log in with MFA Step-by-Step Guide Set Up your MFA Options Open your web browser and navigate to the Microsoft Security Info page: Sign in with your Office 365 Login username and password.