My Apple iPad went dead over night and in the morning I plugged it in. It shows a little battery icon with three red bars so I plugged it in and I thought it would charge for about 4 hours I came back to see how it was. The same thing was on the screen and when I unplugged it from the charger, it flashed that the battery is low and I need to plug it in. So I plugged it back in and ever since it still has that bar with the three bars and will not charge or do anything. I've already held down the home and the other button for 15 seconds, and still it has not started to work and I do not know what to do!
Make sure you are using an official Apple charger. Sometimes the cheap chargers are hit-or-miss. I have a generic lightning cable for an iPhone that I bought at a gas station, and sometimes it works, and sometimes it doesn't.
Sometimes it will notice that it's plugged in, but will not actually charge. As for my knock-off lightning cable, sometimes it depends on which direction I have it inserted (since they fit both ways).
Just play around with it and come back every once in awhile. If all else fails, take it to a Genius Bar.