jupyter notebook changes the label from numeric to [*] and then gives no output

Question

jupyter notebook changes the label from numeric to [*] and then gives no output

When trying to open and run .ipynb file in Mozilla FireFiox the jupyter notebook, then after several clicking on the run button it starts writting [*] instead of [3],[4] etc and no output results afterwards. Please see the image above.

I have tried to reload the jupyter ipynb file and from time to time it works, but mostly it doesn't

I have downloaded ipynb files from this web

EDIT Yes there is