I cannot use my authenticator app after switching to a new phone. I no longer have the previous phone.

Is this your personal account?

If so,

If you’re on the sign-in page and can’t access your authentication app, click “I can’t use my app right now.” Then look for an option like “Show more verification methods” to see if you have a backup (e.g., a phone number or alternate email).

If you don’t have access to any of the options listed, select “I don’t have any of these.” This will begin the recovery process. As part of that process, Microsoft will let you add new contact information — but only after a 30-day waiting period.

This 30-day delay is intentional. It’s a security safeguard designed to protect users in case someone else tries to hijack their account by changing recovery info. The wait gives the rightful owner time to notice and stop unauthorized changes.

Unfortunately, this policy cannot be bypassed. Microsoft explains it further here.

https://support.microsoft.com/account-billing/-your-security-info-change-is-still-pending-or-you-can-t-access-this-site-right-now-microsoft-account-message-cbd0f64f-02d9-45d2-90c3-2375e5a72e52#:~:text=While%20we%20understand%20this%2030,phone%20number%20or%20email%20address.

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If it is work/school account,

Microsoft does not directly manage organization users. Instead, each organization's IT administrator is responsible for managing its users according to its internal protocols.

You should contact your organization's IT support team. They need to reset your MFA for you in order for this to work. Once the reset is completed, follow these steps:

1. Open your web browser and navigate to https://login.microsoftonline.com.
2. Sign in to your account.
3. You will be prompted to set up MFA again. Make sure to update your phone number during this process.

If your organization's IT administrator requires guidance, they can follow these steps:

1. Sign in to the Microsoft Admin Center at https://admin.microsoft.com using their credentials.
2. Navigate to Users > Active Users in the left-hand menu.
3. Select the relevant user.
4. On the user card that appears on the right, scroll to the bottom and click Manage multifactor authentication.
5. On the MFA settings page, locate the user's name, select it, and click Manage user settings on the right.
6. In the pop-up box, check the first box and click Save.

This process will reset MFA for the user, allowing them to set it up again.