Fitbit app unable to connect to my charge3

[SunsetRunner]

After experiencing loss of sync issues, I rebooted my charge3 and reinstalled the Fitbit app. Since then the app fails to connect after recognising my charge3.

[SunsetRunner]

Try a Long Restart:

CHARGE 3 LONG RESTART
Connect the device to the charging cable.
While the device is plugged into the charging cable, press and hold the button down for 15 seconds.
The device turns on and shows a battery icon. Two vibrations occur: first a short vibration, then a medium vibration.
The device turns off.
The device turns on and shows a progress bar and short vibrations occur. The progress bar completes. Note: A total of 7 short vibrations occur.
Remove the device from the charging cable. The device shuts down.
Important: Plug the device into the charging cable again.

[SunsetRunner]

My charge3 didn't behave as described following your procedure. A couple of times charge3 displayed a 4-digit code but when typed in the app said wrong code. After that charge3 didn't get past the stage where app saying device recognised.

[SunsetRunner]

Contact Customer Support.