Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Dear @Dani Larsen
Based on your description, I understand that you are using an education account. In this case, first, I recommend that when signing in, please try to look for options like "Other ways to sign in":
If the issue still persists, since you are using an education account and your school has an MFA setting for your account, I highly recommend you contact your school IT staff directly so that they may reset your MFA settings to your new mobile. You might also ask whether your MFA can be temporarily disabled to allow an emergency sign-in. For more information: How do I find my Microsoft 365 admin?
For that reason, the school IT admin can revoke MFA sessions and require re-registration in Microsoft Entra admin center
For more information and instructions, please ask the school IT Admin to follow the Microsoft Official Guide here: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID | Microsoft Learn
I hope this information is helpful. Thank you for your patience and your understanding. If you have any questions, please feel free to reach out. I'm looking forward to your update.