Gemini API returns 403 for new project despite correct key setup

Gemini API
1

Title: Gemini API returns 403 on new project

Hello, I have a new personal Google Cloud project for a legitimate staging demo.
Project ID: neuralflow-demo-free-5063..

The Gemini API is enabled. The API key is service-account-bound and restricted to Gemini API only. Application restrictions are set to None because the request comes from a Vercel server.

A direct generateContent request to gemini-3-flash-preview returns HTTP 403. The same model works in AI Studio Playground.

Could you review whether there is a pending verification, security restriction, or project-level access block? No sensitive data is involved

2

Hi @Marlon, To resolve this restriction and make API calls from your application, link an active Google Cloud Billing account to your project.