Welcome to OpenAI community.
Usually it takes some time for the file to be ready after it finishes uploading.
The openai.File.create returns the file object which has a status attribute which tells the current status of file.
status:stringThe current status of the file, which can be either
uploaded,processed,pending,error,deletingordeleted.
You can only proceed with fine-tune if the file is processed.
To run fine-tune once the file is processed, you can make an API call to the Retrieve File endpoint with exponential backoff to check the status within the file object it returns, if it’s processed you can run create the fine-tune job.