429 RESOURCE_EXHAUSTED - "Your prepayment credits are depleted" after enabling Billing (Tier 1)

Hello,

I’m having a billing issue with my original Gemini API project.

Project:
language-vibe

Current status:

  • Billing account is linked.
  • Tier 1 is active.
  • Cloud Billing is active.
  • API key belongs to the correct project.

However, every API request returns:

429 RESOURCE_EXHAUSTED
“Your prepayment credits are depleted”

In AI Studio:

  • The project says “Prepayment required”.
  • Clicking “Set up prepayment” only opens a blank black popup.
  • I cannot access the payment page.

Browser console shows CSP/framing errors and a 404 error related to Google services.

I created a brand new AI Studio project with a new API key.
The new project works correctly.

Only my original project is affected.

I have already verified:

  • Billing account
  • Project linkage
  • API key
  • Tier 1 activation

Could someone from Google please check whether the billing/prepayment status of my original project is stuck or requires manual synchronization?

Thank you.