Have u tried a hard reset yet? Just hold the power and home button down at the same time for 5-10 secs. Ur device should reboot and apple logo pop back up again n hopefully u good to go. If that doesn't work, then u need to put it in dfu mode and restore. Here is how to enter DFU mode when iPad plugged up to ur computer,
ENTERING IN DFU MODE
DFU Mode is all timing. Some people say count to 10 and some people say watch the on screen prompts. Well the best and easiest way to put your iPad in DFU Mode is to listen to the chimes your iPad makes when it is disconnected from your computer and when it is connected to your computer it will chime as well. When you hold the Home and Power button simultaneously your iPad will reboot itself making a chime when it disconnects from your computer, now when you hear the next chime sound, you will release the Power button immediately when you hear that second chime while continuing to hold down the Home button until the on screen message prompt says "in DFU Mode wait" then release the Home button. Then restore it thru iTunes.