Hello. I hope you solved this by now, but if not, I know a solution. The issue is the charger cable itself. The same thing happened to me. My Wii U gamepad wouldn't charge because the charger cable stopped working. The best thing you could do is order a replacement, or do what I did- buy a charging base that does not use the original cable at all. I bought an Energizer charging station for $24.99. It has 2 sets of rechargeable batteries for wii-motes (includes charging stations for 2 remotes), and a spot where you put your gamepad to charge.
Caleb Dume: Face The Past