Partial sync can come from Bluetooth ownership, low battery, app permission, background restriction or account/service trouble. Keep data on the tracker while restoring the link. Check whether the tracker appears connected to another device and turn off Bluetooth on that device.
Differential
Likely causes of “Fitbit sync starts but never finishes”, and how to tell them apart
- 1
The tracker is connected to another phone or Bluetooth device
What separates it The sync starts and stalls, and the tracker is paired with a second phone or a tablet nearby.
How to confirm Check whether the tracker appears connected to another device and turn off Bluetooth on that device.
- 2
Low battery on the tracker or the phone interrupts the sync
What separates it The sync fails on a low battery and works after charging.
How to confirm Charge both the tracker and the phone and try again.
- 3
The Fitbit app lacks a permission or is restricted in the background
What separates it The app is not allowed to use Bluetooth or run in the background and the sync stops when the screen locks.
How to confirm Check the app's Bluetooth and background permissions in the phone's settings.
- 4
A stale pairing or an account problem
What separates it The sync fails on every attempt after the other checks, and the device shows in the app as not connected.
How to confirm Remove the stale pairing only as Fitbit directs, and check the account status.
Before you touch a setting
Record this first — changing settings destroys the evidence
- The tracker's time and battery and whether it is connected to another phone.
- The app's Bluetooth and background permissions.
- Where the sync stops and any error shown in the app.
Try in this order
0 of 4 completedCapture the exact symptom
ReversibleCheck tracker time/battery and whether it appears connected to another phone or Bluetooth settings outside the app.
Run the smallest isolation test
ReversibleCharge both, restart tracker/phone and grant the Fitbit app Bluetooth and background permissions.
Correct only the proven cause
ReversibleRemove stale Bluetooth pairing only as Fitbit directs; do not factory-reset before confirming cloud sync/backups.
Verify before changing anything else
ReversibleComplete sync, close the app and confirm a new short walk appears after reopening.
Stop boundary
When this stops being a self-service repair
- !Do not factory-reset the tracker before the sync is confirmed to have failed with the permissions and the link restored.
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Will I lose data if the Fitbit sync does not finish?+
The tracker keeps its recent data until it syncs, so do not reset it. Restore the link and sync again.
Why does sync stall?+
Bluetooth, the app or the account may be stuck.
Should I reinstall?+
If still failing, update the app and try again before reinstalling.