Sorry mate, i probably didn't explain myself very well.
If you view my live home page, and scroll down past the black navbar, my scroll nav bar (white) will then appear. This navbar just has my brand in the middle and then the menu icon to the right. When you click on the menu icon, the drop down list doesn't appear.
As you say, it works when you chose the mobile/tablet view. But i have chose that when my scroll nav bar appears the menu icon shows for all devices including desktop. However, when in designer mode or viewing live, when i click on the icon the drop down doesn't show. In designer, when i click on the nav bar menu the blue outline shows but no content.
I hope this explains things better.