The Lab cannot be opened

I don’t why and what happened on the lab, but same still I tried to open it a couple times and it still not work and I can’t do my assignments.

Please fix it.

Did you re-name your notebook file?

You might need to use the Help menu and install a fresh copy of the notebook.

I did not rename my notebook , it’s just not open and even i tried to reboot it, it still keep rebooting and not open at all.

I just loaded the notebook page, and it worked fine.

Try using the Help menu to get a new copy of the notebook.

It woks fine now. Thank you for helping