How can a Microsoft Store developer with a personal account open a private payout tax support case?

I publish Windows apps through Microsoft Partner Center using a personal Microsoft account. I’m trying to reach Windows Dev Center Support with a question about Microsoft Store subscription payouts.

The Create support case (MSA) link opens Engage Center, but the form fails to load with the error “ReactView frame failed to load.” The general Microsoft Support flow only offered a link to the public community forum.

What is the supported way to open a private Windows Dev Center case using a personal Microsoft account? If there’s an alternative form or support channel, please share the link and the appropriate category for payout and tax reporting questions.

The question I need to route is whether Microsoft withholds U.S. tax on payouts to a Ukrainian sole proprietor for Microsoft Store subscription purchases and renewals by U.S. customers, and which Income Code Microsoft uses in Box 1 of Form 1042‑S if it issues that form.

Thank you.