Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Dear L-138,
Good day! Thank you for reaching out!
I'm sorry to hear that you are having issues with authenticator on new device.
If you have administrative privileges, you may change phone number through Azure portal. If you are not an Admin, you can contact your M365/IT administrator to reset MFA for you through the Azure admin portal. In the Azure portal, the administrator can reset your number, he can remove your old number and resister new one. The admin can also add the number for you through the portal or give you another authentication method.
More info at: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID | Microsoft Learn
If you need guidance on how to find your admin, please refer to: How do I find my Microsoft 365 admin? - Microsoft Support
Also, you may kindly check the following article: Microsoft Authenticator FAQs - Microsoft Support
Also, since we have dedicated support team for Microsoft Authenticator related queries, I'd also recommend you to kindly also post your query to Microsoft Authenticator support Forum via Microsoft Authenticator - Microsoft Q&A Engineers who are dedicated into Microsoft Authenticator with rich experience and more resources can then assist efficiently.
We believe they would conduct in-depth research on the problem you encountered and provide you with more professional assistance.
Thanks for your precious time and your understanding would be highly appreciated.