Has anything happened to the iPad? Recent drops? Recent repairs? What error codes are you seeing?
Follow these steps and report back:
Plug your iPad into your computer. Hold down the power button for 5 seconds, while holding the power button, hold down the home button for 15 seconds. When the Apple logo appears, release the power button until the "Connect to iTunes" screen shows up. Restore from there.
If that fails:
Plug your iPad into your computer. Turn it off. Once its off, hold down power and home buttons for 10 seconds, then release the power button. Your screen will still be dark but your computer should let you know that it sees your phone. Restore from there.
Please let me know if that does or does not work. Also update if there has been recent repair or damage.