Menu bar missing on second screen after El Capitan update 10.11.5
You only get a menu bar on anything other than your primary monitor if you have
System Prefs > Mission Control > Displays have separate Spaces checked.

It's not a setting to idly switch on &amp; off if you have a very specific setup because it can seriously mess up your workflow... I did it once before to test a feature for SE, took me days to get my 12 spaces back together :(