I successfully fine-tuned Google Gemini 2.5 Flash on Google Vertex AI with a small dataset. The model worked correctly, and I was able to test and use it.
I then attempted to fine-tune this model again using a larger dataset with the exact same settings. However, after this second fine-tuning, the model became unusable. When I try to test the fine-tuned model, the button to send/enter messages is greyed out, preventing me from sending any input or messages for testing.
Despite this issue, my account was charged USD 579.33, and the money was deducted from my bank account.
Troubleshooting Attempted:
Google Cloud Support Case: 67356027
I had a video conference call with the support team on February 10, 2026 (Tuesday)
I shared my screen and demonstrated the issue
No policy restrictions were found
No root cause has been identified
Current Status:
I was initially told I would receive a resolution by February 16, 2026. However, the resolution has been postponed 7 times:
February 16, 2026
February 20, 2026, at 03:30 PM IST (UTC+5:30)
February 23, 2026, at 03:30 PM IST (UTC+5:30)
March 3, 2026 at 03:30 PM IST (UTC+5:30)
March 6, 2026, at 3:30 PM IST (UTC+5:30)
March 10, 2026 at 02:30 PM IST (UTC+5:30)
March 16, 2026 at 02:30 PM IST (UTC+5:30)
What I Need:
Escalation Path: How can I escalate this issue to higher management? Currently, all my emails to Google support are being handled by the same representative who has not been able to resolve the issue.
Questions for the Community:
Has anyone experienced a similar issue with Vertex AI fine-tuning where the test interface becomes unusable?
What is the proper escalation path for unresolved Google Cloud support cases?
Are there any known limitations when fine-tuning an already fine-tuned model with larger datasets?
Any guidance or assistance would be greatly appreciated.
Case Number: 67356027