When in responsive mode, eg: on a mobile browser, the 3-bar ‘hamburger’/navbar menu is almost impossible to see.
Touches on the closed discussion here: Open to discussion on responsive tweaks?
The contrast on the Navbar Menu Button is the issue, as previously identified: it’s shades of (dark grey) on top of dark grey.
To see the button whilst on mobile my experience is that you need to disable any screen brightness/power saving controls and pump the brightness to full. Even then in anything above low-ambient-light levels, it’s still difficult to see.
I’m a hack when it comes to this, but I’m going to play with the css to see if I can fix it for myself, definitely needs a correction though 
Thanks.