How to retrieve the administrator account (Microsoft Entra ID)

I have registered a business account in the Partner Center using my personal account and have successfully passed the identity verification. However, I am encountering the following issues and urgently need assistance:

Missing permissions: After logging in, I am unable to access "User Management". The system prompts me to log in using the associated Microsoft Entra ID (formerly Azure AD) credentials.

Lost account: The administrator account automatically generated by the system at registration, ending with .onmicrosoft.com, I did not receive any related records and now I cannot retrieve it.