This may be the same issue as reported here?
I see you are using Anaconda, too and so maybe it is the same.
The OP said reinstalling the Anaconda Distribution entirely helped.
‘fixed’ is a bit of misnomer here. A better way to fix it would be to point it out in the Issues so that the developers can address it in the latest Jupyter tech. It looks like from here at least for Jupyter Notebook 7+ that is in the works, or there is place for you as an interested party to make a plug for the Help menu getting some attention, too.