Gemini TTS returns HTTP 403 “Your project has been denied access” despite active billing

Gemini API
1

When using voice generation in Google AI Studio, running the following Gemini TTS models results in an HTTP 403 error:

Target models:
- gemini-3.1-flash-tts-preview
- gemini-2.5-flash-preview-tts

Error displayed:
Http response at 400 or 500 level, error: , http status code: 403

On the API side, “Your project has been denied access” / PERMISSION_DENIED is returned.

Confirmed details:
- Gemini API is enabled
- Billing is active (Tier 1, Prepaid)
- API key is restricted to the Gemini API only
- The same 403 error is reproduced on another project with billing set up
- No warnings or appeal options are displayed on the Projects or Billing screens in AI Studio
- Google Cloud Billing Support has also confirmed that there are no payment restrictions or permission issues on the billing account and project

Google Cloud Billing Support case:
#73262025

Billing Support advised me that this issue cannot be resolved by billing support and instructed me to post in the Google AI Developer Forum.

Could you please advise on how to check if a Trust & Safety or anti-abuse restriction has been incorrectly applied, and the steps to resolve it?

If necessary, I can provide the request ID, timestamp, and additional logs.

2

Hello @iijima_kimto ,

Getting a 403 API error response and / or seeing “Unavailable” next to your project in AI audio indicates a flag has been placed on your account. To proceed:

  1. Check for banners / error callouts in the AI Studio Projects page & the Billing page. Mostly these flags cause visible banners or other errors on these pages with concrete next steps / appeal links.

  2. If you’re on the free tier with no billing attached, you should consider setting up billing. In most cases this is enough to clear any flag on your account. Please note this will mean you lose your free tier quota.

We apologise if the above doesn’t resolve the problem for you. We’re working to improve our messaging in AI Studio and support processes to handle this better.

3

Thank you for your response.

I have checked both the AI Studio Projects page and the Billing page.

1. No warning banner, error banner, “Unavailable” status, appeal link, or additional instructions are displayed on either page.

2. This project is not using the free plan. Active billing is configured, and the account is currently on Tier 1 with prepaid credit.

3. Google Cloud Billing Support has already confirmed that there are no payment restrictions, billing problems, or permission issues affecting the billing account or project.

Google Cloud Billing Support case:

#73262025

4. The Gemini API is enabled, and the API key is restricted to the Gemini API.

5. The same HTTP 403 error was reproduced in two separate projects with active billing.

Affected models:

- gemini-3.1-flash-tts-preview

- gemini-2.5-flash-preview-tts

Error:

HTTP 403 PERMISSION_DENIED

“Your project has been denied access”

Because no banner or appeal option is available, I cannot follow an appeal procedure from the Projects or Billing page.

Could you please escalate this for a manual Trust & Safety / anti-abuse review, or provide the specific appeal URL or next step for this account restriction?

I can provide request IDs, timestamps, screenshots, and additional logs if required.