Where do you get your list of User Agents that you include by default in the plugin and how often do you update them?
The "high" group doesn't currently doesn't seem to support the Nokia Lumia by default - I guess because it's relatively new.
Just adding "lumia" seems to do it for me.
Here's some more info on Nokia User Agents:
http://www.developer.nokia.com/Community/Wiki/User-Agent_headers_for_Nokia_devices