Over time we have tested and used different patches & some do give varying results but you can usually get them to work. The biggest difference in the pads is the amount of gel/contact quality between electrode and skin. If you are not having the response, I recommend trying to adjust to find the nerve easier. The best way to do this is have the person pretend to give a high five. Then place on the inside of the arm just to the inside of the elbow and slightly above. I've attached pictures of right electrode positions for the controller, controlled and ulnar nerves.

Another thing that may be an issue is that they can feel it, but the strength is not strong enough to generate the movement. I recommend slowly turning up the gain on the TENS device and see if that helps. Lastly, if that does not work please open your TENS device and take a picture of the dial settings.