Trying to login but got MFA issue

Hello @ThanhDN Admin,

Based on your description, you'll need to revoke your MFA access, which will allow you to set up Authentication method on another device and then you can access Microsoft services.

Please check to see if there are other admins in your organization who can help you with the reset.

 Ask your administrator to follow these steps:    

• Go to Microsoft Entra Admin Center: https://entra.microsoft.com  
• Navigate to Entra ID > Users > All Users.  
• Select your user account.  
• Go to Authentication Methods.  
• Click "Require re-register multifactor authentication".  

This will reset your MFA settings. The next time you sign in, you’ll be prompted to set up the Authenticator app again using a QR code.  

If you are the only administrator in this tenant, you will need to contact the Microsoft Data Protection team, as they are the only group authorized and equipped with the necessary tools and verification procedures to confirm your identity and restore administrator access. 

Please try to find the related hotline number to call the frontline and let them raise a ticket for you (select the Work account tab for business phone number support): Customer service phone numbers - Microsoft Support 

Depending on your country or region:

For some countries, when calling the support number, although there are about 30 seconds opening as something "you can visit the link...." But you can ignore this opening and wait until the option, then "1" as a business email user, "1" again for technical help.   

For some countries, it will be an automated conversation like:    

• First, when you call the hotline, it asks what kind of problem you are worried about.   
• Answered: authenticator.   
• A: What kind of product are you using?   
• B: Microsoft 365 for business.   
• A confirmation: education or company account?   
• B: For business
• A: Are you an administrator?   
• B: Yes.   
• A: Do you have the other admin in your organization?   
• B: No.   
• A: You need one.... Service request?   
• B: Yes   

Note:

• You may need to call multiple times before you are connected to a live support representative and can successfully create a support request with a ticket number for tracking. 
• If your subscription is from a partner or reseller, contact the reseller's support provider to help open a service request on behalf of you instead.   

I’d like to clarify that I don't represent Microsoft, I do not have access to user sign-in logs, cannot reset MFA, revoke access, or contact Microsoft Support/Data Protection Team on your behalf. Please consider me an end user as well, providing guidance based on experience and documented processes.

If you encounter any difficulties in contacting the frontline support, please feel free to let me know. Thank you and I wish you a great day!