Hi, sorry for my English, i use translate.
I use Prestashop 1.7.6.2.
I have the same problem, I tried to activate debug mode to know if it showed any error, but I did not receive anything.
I also inspected the page with google developer tools, but it didn't show any errors either.
I found that there is an attribute called "data-original-title", and I realized that this attribute is the one that does not allow clicking on the button:
SOLUTION:
Leave title attribute empty in admin/themes/new-theme/template/page_header_toolbar.tpl line 36
We will find this:
so on line 40, we remove {$btn.help} from the title attribute.
Now the button should work on mobile devices, but the page will not show the help message.