Module 2 - Graded Lab - Submission is giving errors while all unit tests pass

I completed the code for Module 2 - Graded Lab and all unit tests are passing when I run the notebook. But when I make a submission, I am getting errors. I have pasted the full errors below.

Is this an issue with auto grader or something else?

Total Score

Try Again・0/30

Exercise 1

0/10

Failed test case: generate_draft raised LLMError: An error occurred: Error code: 400 - {‘error’: {‘message’: “Invalid value for ‘content’: expected a string, got null.”, ‘type’: ‘invalid_request_error’, ‘param’: ‘messages.[0].content’, ‘code’: None}}.
Expected:
no exception,
but got:
An error occurred: Error code: 400 - {‘error’: {‘message’: “Invalid value for ‘content’: expected a string, got null.”, ‘type’: ‘invalid_request_error’, ‘param’: ‘messages.[0].content’, ‘code’: None}}.

Exercise 2

0/10

Failed test case: reflect_on_draft raised LLMError: An error occurred: Error code: 400 - {‘error’: {‘message’: “Invalid value for ‘content’: expected a string, got null.”, ‘type’: ‘invalid_request_error’, ‘param’: ‘messages.[0].content’, ‘code’: None}}.
Expected:
no exception,
but got:
An error occurred: Error code: 400 - {‘error’: {‘message’: “Invalid value for ‘content’: expected a string, got null.”, ‘type’: ‘invalid_request_error’, ‘param’: ‘messages.[0].content’, ‘code’: None}}.

Exercise 3

0/10

Failed test case: revise_draft raised AttributeError: ‘NoneType’ object has no attribute ‘choices’.
Expected:
no exception,
but got:
‘NoneType’ object has no attribute ‘choices’.

Issue resolved. I saved the notebook and then submitted and it worked fine. I did not realize it does not auto-save on submit!