If you have checked that there are no breaks or splits in the wires under both panels, then it could be an issue with your control box.
If you have a friend with the same pad, try it out using their control box. If it works, then yours probably needs replacing.
Easy enough to get a new one.
http://www.guitarherostore.com/Game-Controllers/DDR-Dance-Pads/Afterburner-Control-Box
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