How can an individual Microsoft Store developer open a support case when Engage Center shows “No Access”?

I’m an individual Windows developer in mainland China. I can access my unpublished MSIX app in Partner Center, but the Windows Developer Support link for personal Microsoft accounts leads to Engage Center and displays “No Access.” The documented direct sign-in link produces the same result.

Could a Microsoft moderator direct me to a private support channel? I’d like to confirm whether my Individual developer account can publish a free app with paid monthly, annual, and lifetime unlocks under Store Policy 10.14. If a Company account is required, can a mainland China sole proprietor business license (个体工商户营业执照) be used for verification?

I can provide account and app details privately if needed.