Welcome to the course!
BTW we’re not supposed to post our solution code here on the forums (or in any other public place), but I realize it does make it easier to debug. I will go ahead and edit your post to remove the code.
You are using np.dot to multiply two row vectors of dimension 1 x m. That will just throw an error because the “inner” dimensions don’t match. Here’s a thread which discusses how dot products work in this regard.