Connection and sync depend on several parts working together: the Bluetooth link, the companion app, phone permissions and background activity, account binding, and any pending device updates. Use the sections below to identify which part needs attention without changing more settings than necessary.
[reference] Title: Pairing Text: The band is associated with the companion app and your device or account. Title: Connection Text: The phone and band currently have an active Bluetooth link. Title: Sync Text: Activity and device data are being transferred between the band and companion app. Title: Binding Text: The band may remain associated with a previously used phone or account until it is removed correctly. [/reference]Quick Connection Check
Start with these basic checks before changing pairing records or app data.
[step] 1. Place the band on its charger for about 30 seconds to wake it and rule out very low power. 2. Turn Bluetooth off for about 10 seconds, then turn it on again. 3. Close and reopen the companion app. 4. Keep the band close to the phone, around 10–20 cm during the connection check. 5. Open the band's device page and start a manual sync if the app provides one. 6. Keep the app open and the phone screen active until the sync attempt finishes. [/step] [tip] If the band reconnects and completes a normal sync, avoid changing additional pairing or app settings. [/tip]Connection & Sync Status
Match the behavior you see with the closest case below. Several symptoms can have different causes even when they all appear as a connection problem.
[troubleshoot] Problem: The band shows as disconnected in the companion app. Cause: The Bluetooth session may have ended or a previous pairing record may be stale. Fix: Toggle Bluetooth off and on, briefly toggle Airplane mode if needed, or restart the phone. Then reopen the companion app and remain on the band device page while it reconnects. Problem: The band appears in the phone's Bluetooth list but not in the companion app. Cause: It may have been paired from the phone's general Bluetooth screen instead of through the companion app. Fix: Forget or unpair the band from the phone's Bluetooth list, then start pairing again from inside the companion app. Problem: The band connects but data sync stalls or does not complete. Cause: The app may have been interrupted, restricted in the background, missing a required permission, or holding temporary cached data. Fix: Keep the companion app in the foreground during sync, review its permissions and background access, then clear only the app cache if needed before trying again. Problem: Sync works mainly while the companion app is open. Cause: Battery, background activity, background data, or app-start restrictions may be limiting the companion app. Fix: Allow background activity, remove restrictive battery optimization, allow background data when applicable, and enable Autostart or a similar option if your phone provides it. Problem: The app reports that the band is already paired or associated elsewhere. Cause: The band may still be bound to a previous phone or account. Fix: If the previous phone is available, remove or unpair the band from its companion app first. If normal removal is no longer possible, consider a factory reset only after the non-destructive options have been tried. Problem: Sync becomes unstable after an update attempt, or the band restarts or freezes during transfer. Cause: A device resource or update transfer may have been interrupted, or the Bluetooth connection may have become unstable during the transfer. Fix: Charge the band well, keep the companion app open, temporarily disconnect unnecessary Bluetooth accessories, and allow any pending transfer to finish. If the behavior repeats, restart the phone, clear the companion app cache, and use a clean re-pair. [/troubleshoot]Pair Through the Companion App
The Xiaomi Mi Smart Band 4 should be added from the companion app's device-pairing flow rather than treated as a normal Bluetooth accessory from the phone's Bluetooth screen.
[dosdonts] Do: Enable Bluetooth before starting pairing. Do: Keep the band close to the phone during pairing. Do: Start pairing from inside the companion app. Do: Confirm the pairing request on the band when prompted. Dont: Create a separate direct pairing from the phone's Bluetooth screen before the app pairing flow. Dont: Leave an old pairing record active when performing a clean re-pair. [/dosdonts]Clean Re-Pair
Use this sequence when the band and app appear to have mismatched pairing records.
[step] 1. Remove or unpair the band from the companion app. 2. Open the phone's Bluetooth settings and forget the band if it still appears there. 3. Restart the phone. 4. Open the companion app and add the band again from inside the app. 5. Complete the pairing confirmation and run a short manual sync. [/step] [note] A clean re-pair removes mismatched pairing records without immediately using a factory reset. [/note]App & Background Settings
For reliable background reconnection and sync, the companion app needs permission to continue working when it is not the active screen. Exact setting names vary by phone software.
[checklist] * Battery setting for the companion app is Unrestricted, Not optimized, or the closest available equivalent * Background activity is allowed * Background data is allowed when a data-saving mode is active * Autostart or automatic app launch is enabled if the phone provides that option * Nearby devices or the Bluetooth-related permission requested by the app is allowed * Location permission is allowed if the phone or app requires it for Bluetooth scanning * Notification permission is allowed when band alerts are expected * The companion app is updated * Automatic date and time are enabled * Automatic time zone is enabled [/checklist]If your phone aggressively closes background apps, a lock or keep-open option in the Recent Apps screen may help during connection checks. Avoid repeatedly force-closing the companion app during normal use.
When Sync Stalls
- Open the companion app and stay on the band's device page.
- Keep the screen on until the transfer completes.
- Avoid switching between apps during an active sync or device update.
- Clear the companion app cache if its device status remains inconsistent.
- After a phone or app update, recheck permissions because some settings may change.
Refresh the App Session
If the companion app continues to show an inconsistent device state, signing out and signing back in can refresh the account session. Reopen the band's device page and try a normal sync afterward.
Clearing the companion app's stored data is a stronger step than clearing its cache because it resets local app settings and may require signing in and pairing again. Use it only after the simpler checks have not helped.
Phone Bluetooth Records
If the phone continues to retain stale Bluetooth information, first remove only the band's saved pairing record. Some phones also expose Bluetooth system cache or data controls.
[warning] Clearing Bluetooth system data can remove other saved Bluetooth pairings from the phone. Treat it as an advanced phone-side reset rather than a normal connection step. [/warning]Keep the Connection Stable
- Keep Bluetooth enabled when you expect background reconnection or syncing.
- Temporarily disconnect unused Bluetooth accessories when checking connection stability.
- If several wearables or audio accessories are connected, establish a stable band connection first before reconnecting other accessories during diagnosis.
- Temporarily turn off aggressive battery-saving modes while checking sync behavior.
- Keep the phone's date, time, and time zone automatic to avoid incorrect data timestamps.
- Avoid frequently closing the companion app from the recent-apps screen.
- Open the companion app periodically for an intentional sync, especially after a day with substantial activity data.
Band-Side Checks
Restart the Band
If the band interface feels slow or connection behavior becomes inconsistent, use its restart option if that option is available in Settings.
If a restart option is not visible, place the band on its charger, make sure it is seated correctly, then remove it and check the connection again.
Check Battery Level
Very low battery can make connection, data transfer, and updates less reliable.
- For normal connection checks, charge the band above roughly 20–30% when possible.
- Before a device or resource update, aim for about 50% charge or more.
- Avoid starting an update while the band is nearly empty.
After an App or Band Update
If connection behavior changes after an update attempt, first allow any pending device or resource transfer to finish before removing the band or resetting it.
[checklist] * Band has about 50% charge or more before continuing an update * Companion app remains open in the foreground * Phone and band stay close together * Unnecessary Bluetooth accessories are temporarily disconnected * Pending update or resource transfer is allowed to complete * Companion app permissions are still enabled [/checklist]If the transfer repeatedly stops, restart the phone, clear the companion app cache, and try again with the app kept in the foreground. A clean re-pair can be used before considering a factory reset.
If the band repeatedly restarts or freezes during sync, reduce other Bluetooth activity around the phone and retry after restarting the phone. Re-pair the band if the same behavior continues.
Changing Phones or Accounts
If the band is still associated with an older phone, remove it from the companion app on that phone before pairing it with the new one whenever possible.
- Open the companion app on the previous phone.
- Remove or unpair the Xiaomi Mi Smart Band 4.
- Disconnect the previous phone from the band.
- Start the pairing flow from the companion app on the new phone.
If the previous phone is unavailable and the band cannot be associated normally, a factory reset may be needed as a final option.
Factory Reset
A factory reset should remain a last step because it can erase data stored locally on the band and requires setup again.
Consider it only when:
- The band remains bound to another phone or account and cannot be removed normally.
- Pairing confirmation continues to mismatch after a clean re-pair.
- The band remains in an unusable post-update state after normal connection checks.
- Connection and sync remain unsuccessful when checked with more than one compatible phone.