There are many reasons your iPad may have stopped working.
The quickest and easiest way to get it back online is with a wipe and reconnect.
To begin to wipe your iPad:
1. Open the Settings
2. Select General
2. Select Reset
2. Select Reset All Content and Settings
2. Select ERASE then ERASE again
Your iPad will then erase itself.
Once it comes back on, follow these steps to get back online