Can you give your code? He has the bar-light class added to the ion-header-bar and is changing this class to be transparent. Make sure you are using that class, if that’s the one you are changing. I was able to see the transparent bar by changing it to an ion-nav-bar in his codepen: http://codepen.io/anon/pen/KwQPeY
It looks like you are using the bar-stable class on your nav-bar, in which case you should be overriding that class instead of bar-light.