429 RESOURCE_EXHAUSTED "prepayment credits depleted" despite active prepay balance

Gemini API
1

Project ID: gen-lang-client-09493981…
Error: 429 RESOURCE_EXHAUSTED “Your prepayment credits are depleted”
Billing tier: Prepay (active for years)
Prepay balance: Rs. 18000+

What works: models.list(), models.get()
What fails: models.generate_content() — all models

API key length: 39 characters
Tested models: gemini-2.5-flash-lite, gemini-2.5-flash — both fail

This is not a code issue. Same setup worked previously.
Please check billing sync for this project.

2

Ive been getting the same issue. Was it resolved for you?

3

AIStudio is separate now from GCP credit where one has to use vertex AI to make API calls. So either fund AIStudio separately or start using vertext AI which will use GCP credits.

4

But ive around a 1000 bucks available in AI studio itself.