Windows Developer Support (MSA) opens blank Engage Center; how can I create a payout/tax support case?

I am trying to open a free, non-technical Windows Developer / Microsoft Store support case for payout and tax profile setup.

Reproduction:

1. Visit the official Windows Developer Support contact page:

https://developer.microsoft.com/en-us/windows/support?tabs=Contact-us

2. Under "Non-technical support (Dev Center programs)", use "Create support case (MSA)".
3. Sign in with a personal Microsoft account.

Sign-in succeeds, and Engage Center displays its header and account menu, but the main content stays empty. No case-creation form or error code appears.

Checks already performed:

• The same result occurs in Google Chrome and another Chromium-based browser.
• Switching Engage Center itself from Simplified Chinese to English does not resolve the blank content.
• Partner Center's "AI assistant and support" displays a message that personal Microsoft accounts are not supported; "Contact customer support" is disabled. Its Windows developer-support link returns to the same Engage Center page.
• The Partner Center support request list contains no case and offers no usable "New request" entry.

What is the supported no-cost way for a personal Microsoft account to create a Microsoft Store payout/tax support case when the official MSA page is blank? Is there an alternative private support channel, or can this portal issue be escalated to the responsible team?

I am only asking about the support access problem here. No identity documents, tax numbers, bank details, seller IDs, or authenticated URLs are included.