Saif has covered the actual programming questions, but the point about why you get 0 points on everything is that you have a compile error. That means the grader can’t get far enough to run any actual tests, since the notebook doesn’t even compile. Anytime something like that happens, you end up with 0 score on everything.
Back to the actual question, here’s a thread which shows the shapes of everything on that particular function. Maybe that will give some clues about where your code goes off the rails. 