My First Project shows free trial credits, but generateContent returns "Your prepayment credits are depleted"

Gemini API
1

Hello,

I am experiencing a billing synchronization issue with Gemini API.

Project Name:
My First Project

Current situation:

  • Google Cloud shows approximately KRW 453,008 free trial credits remaining.

  • Gemini API is enabled.

  • Tier 1 is active.

  • Billing account is connected.

  • models.list requests work successfully.

  • Multiple API keys from the same project have been tested.

However, every generateContent request returns:

“Your prepayment credits are depleted.”

The issue occurs across different Gemini models.

It appears that the API can access the project and API keys correctly, but content generation requests are being blocked as if no credits are available.

Could someone please verify whether the free trial credits are correctly synchronized with Gemini API billing for this project?

Thank you.