Submission issue

It looks like your notebook is damaged somehow: some of the info for the grader (which you can’t normally even see when you run the notebook) is either missing or changed in an invalid way. Did you edit it using some tool other than the Course website?

In any case, you’ll need to get a fresh copy and then carefully “copy/paste” over just your completed work in the “YOUR CODE HERE” sections. There are instructions on the DLS FAQ Thread for how to get the clean copy.