Fine tunes based on GPT-3 models should be considered long-gone. The models have been shut off. models endpoint still returns ada and curie, but calls are 404-model_not_found.
The error in the initial screenshot is 500, usually internal server error. This can happen from API failure to parse the AI output.
A reproducible 500 example is to stimulate a function call with max_tokens=5 or such. A bad fine-tune and its prompt getting a bad function send triggering sequence emitted from a model could also cause this, or the function specification not existing in the API call.