A quick scan of the Fitbit support forums indicates yours is a fairly common issue. Other than a series of restarts, reconnects, etc, I don't see any definitive responses to resolve your matter.
I also saw your other questions there (you have asked the same questions here (TG and TH). I really suggest asking there for assistance with folks more familiar with the devices.
Of note, I noticed you posted the same number sequence (
in your other thread) here and there. Do those numbers remain on the display at all times?