Hi! This extension worked pretty well by spoofing WebRTC ip to your proxy’s one. But recently it just stopped working at all, I didn’t update my browser version (used 52 ESR) or anything, it just stopped working and not spoofing any IP. Please take a look http://ge.tt/5JH9E0m2
Is the add-on listed on AMO? Where did you get it from? Did you try contacting the developer about this?