Tier 1 Paid Key: Persistent "Could not validate topic" error on science prompts (e.g. "Osmosis")

Gemini API
,
1

Hello, I am experiencing a persistent “Could not validate topic” error with the Gemini 1.5 Flash model through the API, despite being on a Tier 1 (Paid) plan.

The Problem: > My prompt (topic: “Osmosis”) works perfectly inside the Google AI Studio UI. However, as soon as I call it via the API in my app, it returns “Could not validate topic.” This is a standard science topic and should not be triggering safety blocks.

Troubleshooting already completed:

  • Billing: Confirmed active and healthy by Google Cloud Billing support.

  • Safety Settings: I have explicitly set all safety thresholds to BLOCK_NONE in my code (Harassment, Hate Speech, Sexually Explicit, Dangerous).

  • API Key: The key is restricted specifically to the “Generative Language API.”

  • Quota: My project shows as Tier 1 in AI Studio.

Technical Details:

  • Model: gemini-3-flash-preview

  • Project ID: gen-lang-client-0269868031

  • Region: UK