The charger may not be supported by your iPad. If your using a charger for a different device or if your using a generic cheap charger than that could also be the problem. I hope this answers you question!
Scosche Revolt, 2 x 12 watts will allow your to charge 2 iPads. Make sure you get a charger that can handle 2 10 watt devices and you are as good as gold. It will handle any 2 USB devices you can throw at it.