The last assignment of the TF2 course in week 4 -Graded 0/100

I submitted my assignment yesterday and achieved over 99% accuracy for training and about 95% accuracy for validation within 15 epochs. However, I received a grade of 0 points from the grader, which was quite unexpected.
I suspect that one possible reason for this could be that I had to add a new cell to my code.but without adding it did not work.
Do you think there are any reasons for the failure of my assignment?

Thank you in advance for your assistance.
Best regards,

What do you mean by?

That’s generally a bad idea, and probably not really necessary.
It can confuse the grader.