iPad 3 charging adapter not supported.
I'm trying to charge my iPad 3 (wifi only) using the A/C charging adapter that came with the iPad, but I get the message "This accessory may not be supported." Why am I getting this message? The battery icon at the top of the screen says "Not charging.", or shows the battery level in white, as opposed to green when charging. The iPad still charges under these conditions, but very slowly.
iPad 2, iOS 8.3