FaceTime

Read here => If you get an error when trying to activate iMessage or FaceTime - Apple Support

Have you tried a reboot of your iPad? If your iPad has a home button on it, press and hold the Power/Sleep button and the Home Button till the iPad shows the Apple Logo on the screen. If you get a message asking you to swipe to turn off, just continue to hold both buttons till you see the Logo. Once you see the Logo you can release both buttons and allow the iPad to continue booting up. Once it is back up it has been restarted, check again to see if you can get FaceTime to load at that point.