Gemini Image Generation Refusal Error Fix: Cause-Specific Diagnosis Table and 5-Step Recovery

Error Messages and Immediate Checks

When requesting image generation in the Gemini app, "Cannot generate image" or "Blocked due to policy violation" appears in red text at the chat window bottom. Thumbnail placeholders turn gray, and download buttons deactivate. Immediately verify three items: first, check if the left sidebar model display shows Flash-Lite(Nano Banana 2 Lite) or Flash/Pro(Nano Banana 2). Second, review account profile for Google AI plan (Plus/Pro/Ultra) subscription and age verification status. Third, scan prompts for prohibited keywords like "nudity", "violence", "real name", or "medical advice".

4-Row Diagnosis Table

5-Step Recovery Procedure

1. Access gemini.google.com, log in with Google account, click the left sidebar menu icon, and select "Gemini 3.5 Flash" or "Gemini 3.1 Pro" from the "Model" menu. Flash-Lite mode blocks reference images and edit requests, so switch to Flash or higher.
2. Enter specific prompts like "Draw: Clean bar chart for business presentation, blue theme, horizontal axis quarterly sales, vertical axis in ten billion won" and submit. Pre-check for prohibited keywords.
3. Hover over generated thumbnail and click "Download original size". Verify file extension is .png and resolution is 1024x1024 (free) or 2048x2048 (paid).
4. Check Google AI plan status via profile icon → "Google AI Plan" menu. If free, select "Join Plus" (₩7,500/month) to unlock 2K resolution and doubled usage.
5. For workspace/school accounts, confirm image generation permissions via admin.google.com → Apps → Additional Google Services → Gemini app. Request activation from admin if disabled.

Verification After Recovery

After following steps, confirm three conditions: first, model display remains "Gemini 3.5 Flash" or "Gemini 3.1 Pro". Second, test prompt "Draw: White circle on blue background" generates thumbnail within 5 seconds with active download button. Third, downloaded PNG file properties show 1024x1024 (free) or 2048x2048 (paid) dimensions.

Unresolved Cases

If blocked persists after steps, submit to Google Support (https://support.google.com/gemini/contact) with: error time (UTC), email, plan type, model settings, full prompt text, and screenshot. Alternatives: 1) Test Gemini 3.1 Pro via Google AI Studio(aistudio.google.com). 2) Generate low-detail sketches with Nano Banana 2 Lite and edit locally. 3) Enterprise users: Contact Gemini Enterprise sales (https://cloud.google.com/gemini-enterprise) for policy adjustments.

Commonly Overlooked Conditions

1. Under 18 accounts cannot edit images (partial edits/remixes). Editing attempts trigger "18+ required" messages, wasting limits.
2. After daily Nano Banana 2 limit exhaustion, Pro regeneration button deactivates. Repeated Pro attempts without awareness accumulate "quota exceeded" errors without results.

Final Recommendations

Free personal accounts under 13: Switch models and remove keywords for 1K resolution. Paid accounts (Plus/Pro/Ultra) with 2K issues: Verify subscription status and renew. Workspace/school accounts: Request admin activation of image generation and age limit removal. Personal account workaround: Use personal account until admin approval.