This support request concerns a different existing Microsoft 365 tenant

Disclaimer: As this forum is in the Russian (ru-ru) locale but your question was posted in English, I will respond in English to ensure accuracy.

Dear @Golden Green Group

Based on the information you provided, I understand that your admin account has been blocked and you are currently unable to complete the authentication process required to access the account. However, as a forum participant, I cannot access Microsoft systems, verify tenant ownership, escalate cases, or reset MFA registrations on any tenant.

For a sole Global Administrator MFA lockout, Microsoft's Data Protection / Tenant Recovery team is the only team authorized to verify ownership and assist with restoring access to the tenant. Therefore, please contact Microsoft Support by phone and request a tenant recovery / sole Global Administrator MFA lockout.

For a full list of regional numbers, you can also visit this official page: Customer service phone numbers - Microsoft Support. The support team will assist you as soon as possible. For reference:  Get support | Microsoft Docs   

Note: You may also consider calling a Microsoft support number for a different region if support in your local region is unavailable or unable to route your case appropriately.

(While calling, you may hear an introduction of about 30 seconds such as "you can visit the link...". You can ignore it and wait until you are presented with the options. Then press "1" as a business email user, and again "1" for technical help.)      

Here are some tips and an example of a prompt to help you navigate the IVR more effectively: 

In some countries, it is an automated conversation like: First, when you call the hotline, it will be asked as follows: 

IVR: What kind of problem are you concerned about? 

You: Authenticator. 

IVR: What kind of product do you use? 

You: Office 365 for business. 

IVR confirmation: education or company account? 

You: For companies 

IVR: Are you an administrator? 

You: Yes. 

IVR: Do you have the other administrator in your organization? 

You: No. 

IVR: Do you need a... Service request? 

You: Yes  

This process should connect you with a live agent who will create a service request with the Data Protection team. They will then contact you to help you regain access. 

If the automated phone system does not get you to a human agent, one workaround is to create a separate trial Microsoft 365 tenant and use that tenant to open a support ticket on behalf of the locked tenant.

• Sign up for a new Microsoft 365 Business trial using this link: Compare All Microsoft 365 Plans. You will need to use a different, personal email address to register. 
• Once the trial account is created, log in to its Admin Center > From the Admin Center, open a new Service Request. For reference:  Get support | Microsoft Docs   
• In the ticket description, explain that you are locked out of your primary tenant (your.onmicrosoft.com) and that you need to speak with the Data Protection team to regain access.
• Remember to provide your locked account's details and a good contact number for them to reach you. 

Important: Please remember to cancel the trial subscription after your original account issue is resolved to avoid any future charges. 

When creating the support request, I also recommend disabling or bypassing the AI/Support Assistant option if presented and choosing the path that allows you to contact a support engineer directly.

I hope the information shared is helpful. If you have any questions, please feel free to reach out. I'm looking forward to your update.