Lately I had a huge problem with nav-bar style. It didn't work on my new site. It took a long time for me to find the way to do this.
I opened superfish-navbar.css and there I found:
"adding the class ext-navbar in addition to ext-menu creates an all-horizontal nav-bar menu"
And solution was easy:
go to module configuration and add "ext-navbar" for "Menu Class Suffix" option.