Startups: Companies that are in their initial stages of business and typically developing a business model and seeking financing.
I think Azure subscription management support is the next step. You can try opening a request without a subscription or activating pay-as-you-go. Azure portal → Help + support → Create a support request → Subscription management.
Ask for a sign-up eligibility review or help reaching the right team. Include the exact error and mention that Startups Program Support is unavailable.