Tier 1 Postpay project returns 429 "prepayment credits are depleted" despite active postpay billing

My project is Tier 1 Postpay with an active linked Cloud Billing account and a valid card, but every generateContent call (gemini-3.1-pro-preview AND gemini-2.5-flash) returns:

429 RESOURCE_EXHAUSTED — “Your prepayment credits are depleted.”

Details:

  • Project number: 17714083..
  • Project ID: sanguine-stock-501417-..
  • AI Studio shows “Tier 1 - Postpay”; billing linked, active, valid card
  • Developer Program credit ($14.18) is Available on the billing account
  • ListModels (GET) succeeds; only billed generateContent calls fail
  • Persisted 6+ hours; a fresh API key did not help

This matches the known incident where a backend bug switched postpay accounts to prepay (confirmed by staff, resolved by reverting to postpay). Requesting a manual billing sync and a revert of the erroneous prepay switch. Thanks.