Organization enrollment withdrawn – "already a member" – can't identify the Account Holder (Case 103016501599)

Hello,

I am the owner and managing director of a small company in Belgium (Lebi Worldwide) and I am trying to join the Apple Developer Program as an Organization in order to sign and notarize macOS apps with a Developer ID (direct distribution, no Mac App Store).

My organization enrollments were withdrawn with the message that the company is already a member of the Apple Developer Program and that I should contact the Account Holder of the existing membership. The problem is that I do not know who the Account Holder is, and none of the Apple IDs I have access to is associated with any membership (the account page only shows "Join the Apple Developer Program").

I have already submitted a request for further assistance on my existing case (Case 103016501599), but I have not received any reply yet.

Has anyone been in the same situation? Specifically:
• How can I find out which Apple ID is the Account Holder of an existing membership for my company?
• What proof of authority does Apple usually ask for to recover the membership or to have the Account Holder role reassigned?
• Is there a faster way to get a case like this escalated?

If an Apple staff member can look at the case above, I would be very grateful.

Thank you in advance for any advice.