tl;dr: Faulty purifycss configuartion in the gulp.babel.js file.
I also had this problem. My setup:
I can get the responsive dropdown menu to work by using the tab and enter key. This means that the relevant js files are being loaded correctly. The navigation 'burger' also does not appear.
Upon using the chrome dev tools to inspect the responsive dropdown menu example from the foundation website, I noticed that style of <button class="menu-icon" type="button" data-toggle=""></button> is being effected by the .menu-icon CSS rule from the scss partial, _menu-icon.scss. Mine wasn't. When I looked, the foundation.scss file from the app/ has the exact same style rule. The converted foundation.css was being served from the .tmp/ folder, but did not have the .menu-icon CSS rule. Then I suspected purifycss again (which I had commented out of the gulp file before and forgot to reset the gulp serve, saw no fix and thus falsely excluded the purifycss rule from the list of suspects).
I set my gulp styles task up like this:
gulp.task('styles', () => {
return gulp.src('app/styles/*.scss')
.pipe($.plumber())
.pipe($.sourcemaps.init())
.pipe($.sass.sync({
outputStyle: 'expanded',
precision: 10,
includePaths: ['.']
}).on('error', $.sass.logError))
.pipe($.autoprefixer({browsers: ['> 1%', 'last 2 versions', 'Firefox ESR']}))
/*Stupidly assumed that purifycss supported jade files as src files*/
.pipe($.purifycss(['app/**/*.js', 'app/*.jade']))
.pipe($.sourcemaps.write())
.pipe(gulp.dest('.tmp/styles'))
.pipe(reload({stream: true}));
});
Which meant that the necessary styles were being deleted (including .menu-icon). I think I will use stylperjade or rearrange the tasks so that I can do this: .pipe($.purifycss(['app/**/*.js', '.tmp/*.jade']))\
Let me know if this was your solution as well