This may help some people. I use a VPN for connecting to the Internet. When I use URL Snooper with the VPN connected it fails to find my adapter.  When I switch the VPN off and traffic is routed normally (rather than via a third party IP address) the Network Adapter is found by URL Snooper no problem at all. It's clear that (in my case at least) the use of a VPN (or possibly a proxy server) is creating problems with adapter detection.

I hope this helps some of you or at least shows you where to look.