Gemini API 403 PERMISSION_DENIED — generateContent denied while models.list returns 200

Gemini API
1

Hello Gemini API Team,

I am requesting a review of Gemini API access for my Google Cloud project.

Project name: ofisteapp1
Project ID: proud-skein-509513-..
Project number: 10270421651..
Billing: Free Tier / no billing account attached

I am developing a legitimate business application and would like to use the Gemini API during development on the Free Tier.

I have completed the following checks:

  • 2-Step Verification is enabled on my Google account.
  • A new Gemini API key was created after enabling 2-Step Verification.
  • The key is an authorization key bound to a service account.
  • Google Cloud Console shows the key restricted to Gemini API only.
  • Gemini API is enabled for the project.
  • GET /v1beta/models returns HTTP 200 and lists the available Gemini models.
  • gemini-3.8-flash is listed and supports generateContent.

However, a direct native Gemini API request to:

POST /v1beta/models/gemini-3.8-flash:generateContent

returns:

HTTP 403 PERMISSION_DENIED

Your project has been denied access. Please contact support.

Google AI Studio also shows the project’s Billing Tier as Unavailable.

Because models.list succeeds and the native generateContent request itself returns the project-denied error, this does not appear to be caused by my application code or provider integration.

Could a Google team member please review whether there is an account/project restriction preventing generateContent access and advise whether Free Tier access can be restored?

I would prefer to remain on the Free Tier during development if possible.

Thank you.