Lab kernel is not connecting or not opening

The lab is not opening in my system. either it says the kernel not connecting or doesn’t open.
Please help.
I have tried opening labs with different systems but facing the same problem.

Hi @vyomrastogi ,

What is the name of the lab that is not working?
And if possible can you get the Lab ID?

Hi @SamReiswig ,
I was not able to use any optional lab, as I was not able to see any cells in the Jupyter notebook.
I don’t know how, but now I am able to see and use the optional labs completely.