Hi @Mohammadamin,
From your screenshot, it seems to me you were running the lab on your own environment. Please be noted that the lab is only tested to run on Coursera, so I suggest you to check out the lab on Coursera for your study.
However, if you have the same problem running the lab on Coursera, please follow these steps to refresh the notebook. I have just tried this out myself and it worked.
Raymond