After you engage the Wah and you are hearing sound, does the wah respond to the pedal movement? In other words, do you hear the wah effect when you move the pedal?

If not. that suggests that the toe switch of your pedal is working but the ability to detect pedal movement is not. This will require a trip to your local Line 6 service centre for a hardware repair:

http://line6.com/service_centers/

If you are able to hear the sound responding to the wah effect as you move the pedal, then there is some other problem. Let us know.