Hi
1/ Might I reconfirm whether you are also the Global Administrator of the tenant that is not affected, and whether you can access the Microsoft Admin Center with this account?
If yes, you can follow the steps below to contact Microsoft Engineering Support so that they can help investigate the affected tenant.
- Sign into the "Microsoft Admin Center"
- After clicking on "Help & Support" button like this image, you can type "I need agent support via phone or email". After that, you can click on "Contact support"
- Choose contact method: "Phone"
- Fill all the information in this contact support details, please describe your situation carefully so they will have enough information to help you.
- Finally, clicking on "Contact me"


After that, they will contact you via email to schedule a direct support appointment
*Please remember to cancel the trial subscription once your issue is resolved to avoid any unintended charges.
2/ If you cannot complete the above steps, the Microsoft Data Protection Team is the only team that can provide further assistance. Contacting them directly is the only available path to regain access to the tenant.
Contacting Microsoft Data Protection team by phone support
In this situation, the Microsoft Data Protection team has tools and processes in place to verify identity and regain access to administrator accounts.
Therefore, if you are the only administrator in your organization, then you need to involve Microsoft data protection team. Please try to find the related hotline number to call the frontline let them raise a ticket for you: Customer service phone numbers - Microsoft Support
If you can use English, you may prefer these numbers:


(Important Note: Depending on your country or region, when you call the support number, you may hear an introduction of about 30 seconds such as "you can visit the link...". You can ignore this introduction and wait until you are presented with the options. Then press "1" as a business email user, and again "1" for technical help.)
In some countries, this is an automated conversation: First, when you call the hotline, they will ask you what kind of problem you are struggling with.
Answer: Authenticator.
A: What products do you use?
B: Office 365 for business.
Verification: Education or company account?
B: For companies
A: Are you an administrator?
B: Yes.
A: Are there any other administrators in your organization?
B: No.
A: I need one.... Service request?
B: Yes
If your organization's Office 365 Business subscription is from a partner or reseller, and the global administrator is unable to open a service request on your end, contact the reseller's support provider to help open a service request on behalf of you instead.
Please try "2 or 3"times until you can reach out to an agent.