Q: iPad Air 2 not showing Facebook notifications.

First try a reset. Press and hold both the home and power buttons until the Apple logo appears. Release both buttons. Wait untit your iPad starts on it's own.

If the reset doesn't fix the problem try deleting and reinstalling the Facebook app.

read this thoroughly first, then act > If an app you installed unexpectedly quits, stops responding, or won’t open - Apple Support

Ships that pass in the night, and speak each other in passing, only a signal shown, and a distant voice in the darkness;

So on the ocean of life, we pass and speak one another, only a look and a voice, then darkness again and a silence.

     - Henry Wadsworth Longfellow

It happens. Brilliant minds something something something.