Charge 3 won't sync and stops keeping track of exercise distance in the middle of routine

[TJW21]

My Charge 3 won't stay synced with my iPhone. I've done everything I can find to make that happen (connected it to the charger to reboot and rebooted from settings.) I'm suspecting that this could be the reason why it stops keeping track of my distance on the treadmill right in the middle of the distance that I've set it for and it goes back to the front screen,

[DramaQueenDiva]

Is there a firmware update available for the Charge 3 that needs installing?  Have you updated the Fitbit app?

[JJC80]

mine was updated a few days ago. It worked perfect before. It is now junk. first it started flipping around to different screens on it's own. Now the only screen is a smile face when the battery is full. everything else is just black and will no longer sync.

[TJW21]

Where do I check for a firmware update? I update the app every week if it needs to be.