Error invoking model response: Forbidden

I am facing the same error
not sure why the chat gpt models request parameter is not sent properly while sending request from Drupal chatbot

The AI recipe for the Drupal CMS project contains working configuration for an AI Chatbot: it migt be worth in the first instance looking there to see if you can identify any issues with your set-up.

The code that gives that particular error message has the comment "// Anything else is probably due to a bad request." so it would sound like the issue is with how you've set it up.

I had the same problem. To fix it, I went to OpenAI's dashboard, then I went to Projects > Limits > Allowed models, and finally enabled the model "omni-moderation-latest".