unable to verify using MFA

Hi @LG

The available recovery options depend on the account type.

1.If you are using a work or school account (@domain.com or @onmicrosoft.com)

If you are the only Global Administrator and are completely locked out of the tenant due to the MFA issue, only the Microsoft Support team can assist with regaining access. You might need to contact them via phone service number: Customer service phone numbers - Microsoft Support. The agent will be able to create a ticket for you under the affected tenant and then transfer this ticket to Data Protection team who could help you to regain access.  

When a call is made to support, the first step is to provide an automated voice response from AI. Be careful, you won't be able to speak to a support representative if you don't respond appropriately here. 

Here's an example of a response that actually led to a support representative. Please refer to it:

Q. Can you tell me if you are calling as a home user who uses a product or service at home or a business user who uses it in your business to provide the best assistance? 
A.I am a business user. 
Q. Thank you. Can you give me the details of your inquiry? 
A. Login technical support. 
Q. First of all, can you tell me which products you are inquiring about today? 
A. Microsoft 365 business Standard。 
Q. Please wait a moment, I understand Microsoft 365. Are you calling about a new case or an existing one? 
A. New. 
Q. To receive phone support, your phone number must be associated with your Microsoft 365 admin profile. To do this, go to aka.ms/m365profile. Again, it aka.ms/m365profile . This can take 48 hours. In the meantime, you can go to aka.ms/m365profile and file a case online. If you prefer, you can also text the link to the phone number you are calling. What do you think? 
A. The phone number is already linked to the link. 
Q. Can you tell me about the products in your inquiry? 
A. Microsoft 365 Business Standard. 
Q. Are you a Global Administrator? 
A. That's right. 
Q. I'm sorry. I didn't understand. Are you a global administrator for your domain? 
A. Yes, I am a global administrator for the domain. 
Q. If you have any inquiries, you can contact a Microsoft representative. Are you sure? 
A. Yes. Please. 
Q. Yes, I understand. Please wait a moment.

Please note that this team is always overwhelmed, so you might need to wait for them to call you, this should take 3-10 working days. I know that this is not a convenient solution to hear but it seems to be the only way, and it's recommended that you should have a secondary/backup Global Administrator to fix this issue on your own.    

In case the phone line is not supportive, you can consider directly submitting a support request as a helpful workaround: 

-Create a temporary Microsoft 365 tenant using a trial license: Go to Microsoft 365 Business Plans and Pricing and click Try for free to set up a temporary Microsoft 365 tenant with a trial license.    

-Use this new account to sign in to the Microsoft 365 Admin Center and submit a support request on behalf of your primary (locked) account.   

-Click Help & Support

-If Support Assistant opens, toggle/turn off the Support Assistant option.

-In the search box, type Support and click →.

-Look for and select Contact support.

-You should then be given the option to choose your preferred contact method, such as Email or Phone.

For further instructions, you can follow this guide: Get support - Microsoft 365 admin | Microsoft Learn.   

2.If you are using a personal Microsoft account (@outlook.com, @hotmail.com, @live.com), you can try one of the following options: 

-Use the Microsoft Account Recovery Form: Help with the Microsoft account recovery form | Microsoft Support 

-Alternatively, contact Microsoft Support: Go to Contact - Microsoft Support, > type "Support" and click Get Help, > click Sign in to contact support at the bottom of the > page under Products & Services, select Microsoft 365 & Office > under Subcategory, select Support, > choose Chat with a support agent in your browser.

If you cannot use any of the available verification methods, Microsoft Support will be in the best position to determine what account-recovery options are available.

I hope this helps.