There are actually a couple of things you can do to troubleshoot this problem. Which are listen below...
Solution 1:
Navigate to Settings>FaceTime and complete the following checklist.
1) Make sure FaceTime is checked on.
2) Make sure an Apple ID is connected.
3) Make sure there is an Apple ID where you can be reached via FaceTime
Solution 2:
Navigate to Settings>General>Restrictions and make sure there is nothing that restricts the use of FaceTime or communication.
Solution 3:
Log out of ICloud and your Apple ID, then log back in.
Solution 4:
Plug your device into a computer, open iTunes then back-up your device if you haven't already. Proceed in restoring your device to factory settings, then if needed backing it up.
Solution 5:
If none of the above solutions work, visit this link:
iPad - Official Apple Support