Microsoft Store Company registration for a sole proprietor in Japan and Engage Center “No Access”

I have an active Individual Microsoft Store developer account. I want to publish apps under my existing trade name as a sole proprietor (個人事業主) in Japan. The Company registration flow asks me to use a different Microsoft account because my current account is already enrolled as Individual. When I tried creating a separate Microsoft account, Microsoft blocked the sign-up with error AADSTS7005106.

For a Japanese sole proprietor, is a notification of business commencement filed with the tax office (開業届) accepted for Company verification? Can I keep my current publisher display name on the new Company account?

I already have a support case. I received an automated acknowledgment and sent a follow-up email several days ago, but I still haven’t received a reply. The developer support link redirects me to Engage Center, which shows “No Access.” How can I follow up on the existing case privately with the Microsoft Store developer support team?