Manual billing sync request: 01484A-953F91-255B.. — "Inactive or unsupported" despite funded Prepay balance

Gemini API
1
  1. Billing Account ID: 01484A-953F91-255B..
  2. Project IDs: gen-lang-client-00346636.. (Gym Guide), gen-lang-client-0621002066 (Default Gemini Project)
  3. Description: Cloud Billing confirms ₹539.88 credit balance in Prepay - AI Studio and ₹0 due in Postpay, but AI Studio is stuck on “The billing account type is inactive or unsupported”. Please manually trigger a sync.
2

A credit card that had the permission to approve e-mandate was to be added to resolve the issue. But this thing is not clearly mentioned on the console. After adding the card as primary account, the billing accounts became active again.