Unplug your iPad, if it's charging. Otherwise you won't get the information about battery usage.
If it is unplugged, use it a bit longer, maybe half an hour, then check it again.
If it still doesn't show the data, reboot your iPad: press and hold Home and Power button until you see the Apple logo. Release both, the iPad will power up on it's own.
Another option would be to update your device, if the latest iOS is not installed: 9.2.1.
If nothing of the advice above helps, go to Settings - General - Reset, and select "Reset All Settings". This won't remove any data from your iPad, but it will revert your settings to default. So you'll have to look at the Settings app afterwards, to make sure everything is set up as preferred.