Situation: You may have a problem to use Fitbit device because it doesn’t pair Bluetooth no matter what you try such as disable/re-enable Bluetooth, turn off/on app, restart phone.
Resolution 1: Restart Fitbit device.
Go to the Settings.
Go to Reboot
Press Screen for 3 seconds to restart it.
Resolution 2: Clear User Data or Factory reset – Note: you will lose all tracking data.
Repeat above steps until you see Clear User Data.
After clearing the data, you may need to reset Fitbit.
Please view this step by step video: