Have tried a different cable or charger. Have you tried plugging it into a wall and computer. If trying these does not work, then it is possible that the battery could be gone and you may need to have it replaced.
It could be several factors. Most probably an aging battery starting to fail... Try with another charger (USB ports on a computer could not provide enough amps): if you have the same issue is the battery
Try using the original piece that plugs into the wall and the original cable that came with your iPad Air. The setup you are using now may not draw enough power. The cable could also be a bad cable. Hope this helps!