Problem with week4 lab

Hi there!
I submitted week4 lab but i always get 0 grade. However, all the answers that i computed in jupyter notebook are the same as in “Expected output” field!

cleared the cache, used incognito and different browser and without VPN, etc. but nothing helped
Both my answer and expected output are the same in all the examples

There was a problem compiling the code from your notebook. Details:
name ‘reject_nh_z_statistic’ is not defined

Probability & Statistics for Machine Learning & Data Science → Week 4 → A/B Testing C3_W4_Assignment Lab ID: kdqrhbisgiqh

I get the same problem, even after using # grade-up-to-here

UPDATE!!!

I resetted the notebook and the problem has been solves

How to refresh the notebook