Thank you very much for reaching out and for clearly explaining your situation.
Given that the previous administrator is currently unresponsive, the most effective and appropriate next step is to contact Microsoft Support directly for account recovery and verification. In situations like this, the Microsoft Data Protection team has specialized tools and established processes to verify account ownership and help organizations regain access to their administrator accounts securely.
Please try to find the related hotline number to call the frontline and let them raise a ticket for you: Customer service phone numbers - Microsoft Support
Here are some tips and an example of a prompt to help you navigate the IVR more effectively:
(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 regions, the initial interaction may be automated, so here’s a general idea of how the conversation might go to help you prepare:
What kind of problem are you experiencing?
Answer: Authenticator
What products do you use?
Answer: Office 365 for business
Is this for an education or company account?
Answer: For companies
Are you an administrator?
Answer: Yes
Are there any other administrators in your organization?
Answer: No. I am the only admin in my tenant
Do you need a... Service request?
Answer: Yes. I need to create a ticket. Please send me direct to the Data Protection Teams.
During the phone call, you will need to provide the information associated with your subscription, such as your company name, billing details, phone number, and an alternate email address, etc. This information allows the Data Protection team to verify your identity and securely assist you in regaining access to the administrator account.
While I don’t have the ability to intervene directly or modify account settings from here, guiding you to the appropriate specialized support is the most reliable way I can assist from my role. If you have any updates, or if additional questions come up along the way, please feel free to reply to this thread. I’ll be more than happy to continue assisting wherever possible.
Thank you again, and I hope this helps move things forward smoothly for you.
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