Why is my Fitbit not tracking my sleep?

Picture this scenario: You wake up feeling groggy and sore, even though you didn’t do much of a workout the day before. You tossed and turned a lot during the night and can’t figure out why. The first thing you do is check your sleep tracker for insight. But the data it provides is inconclusive. This is a frustrating situation that has probably happened to you or someone you know.