Android : Trying to capture Android web traffic using Fiddler - "webpage is not available"

I've been trying to setup a proxy connection with my Nexus 5 using this tutorial - http://www.cantoni.org/2013/11/06/capture-android-web-traffic-fiddler

My PC and my Nexus are both connected to my personal wifi.

No matter where do I browse to I'm getting an error - "The webpage is not available".

Any thoughts?