429 "prepayment credits are depleted" despite valid key — countTokens 200, generateContent 429

Gemini API
1 
Subject: 429 "prepayment credits are depleted" — countTokens works, 
         generateContent blocked

I'm getting a persistent 429 on all generation calls, while free calls 
on the same service and model succeed.

Error:
  429 RESOURCE_EXHAUSTED
  "Your prepayment credits are depleted. Please go to AI Studio..."

Diagnostics (same API key, same model gemini-flash-lite-latest):
  ListModels                -> 200 (50 models visible)
  countTokens               -> 200 (works — free, same GenerativeService)
  generateContent           -> 429 (blocked)
  v1beta/interactions       -> 429 (blocked)

Only billable calls are refused. The key clearly has valid permission 
on this exact service, so this looks like a billing-sync issue rather 
than a configuration problem on my end. Three separate API keys 
produced identical results.

Project number: 7862182856..

Could someone please run a manual billing sync for this project?
2

Hello @Rishabh_Sisodiya ,

This happened because Project 78621828**** is on free trial billing account, and the credits cannot be used for Gemini API usage: https://ai.google.dev/gemini-api/docs/billing#cloud-credits