Grading Failed Error on submitting notebook

I am not an NLP mentor, but the notebook mechanisms are the same as in DLS. When I’ve seen students with that error in DLS, it means that there is something structurally wrong with the notebook. Have you used any external tools other than the course website to modify the notebook? The notebooks are JSON files and there is a lot of hidden code that the grader uses and it looks like some of that has been modified or damaged.

My suggestion would be to try getting a clean copy of the notebook and then carefully “copy/paste” over just your completed code from the “YOUR CODE HERE” segments and see if that helps with this error.

Here’s the “clean copy” procedure from DLS, but it’s the same in NLP.