Xiaomi Mi Smart Band 4 Troubleshooting: Not Connecting or Syncing

What “Not Connecting” Usually Means

On Mi Smart Band 4, connection problems typically fall into one of these patterns:

The band is paired, but shows disconnected and won’t reconnect
The band connects, but syncing stalls or fails
The band connects only when the app is open
The band connects for calls but won’t sync activity/health data
The band appears in Android Bluetooth settings but not in the companion app

The fastest fixes come from identifying which layer is failing:

Bluetooth link layer (phone ↔ band)
Companion app layer (app permissions, background restrictions)
Account/device binding layer (band tied to a previous phone/account)
Firmware/resource layer (update issues blocking normal sync)

Fast Recovery: The 90-Second Fix Sequence

Use this sequence first. It solves a surprising number of problems without deeper steps.

Put the band on its charger for 30 seconds (stabilizes power and wakes it)
Toggle Bluetooth off for 10 seconds, then on
Force close the companion app and reopen it
Keep the band within 10–20 cm of the phone
Trigger a manual sync from the app device page

If it reconnects and syncs, you’re done. If not, go deeper below.

Identify Your Symptom and Use the Right Fix

Symptom A: Band Shows “Not Connected” in the App

This often means the phone can’t establish a stable Bluetooth Low Energy session.

Fix A1: Reset the Bluetooth Session

Turn Bluetooth off and on
Turn Airplane mode on for 10 seconds, then off (this resets radio states)
Restart the phone

Then open the app and wait on the device page for a minute.

Fix A2: Remove Ghost Pairings

Ghost pairings happen when Android remembers the band but the app thinks otherwise.

Steps:

Android Settings → Bluetooth
If the band appears as a paired device, tap it → Forget/Unpair
Go back to the companion app and reconnect from there

Important rule:
Pair the band through the companion app first, not directly through Android Bluetooth pairing screens.

Fix A3: Clear Bluetooth Cache (Deep Fix for Stubborn Cases)

Some phones get stuck with corrupted Bluetooth data.

Steps:

Android Settings → Apps → Show system apps
Find Bluetooth or Bluetooth Share
Storage → Clear cache
If still failing, Clear data (this resets Bluetooth pairings on the phone)
Restart the phone
Pair again through the companion app

Symptom B: The Band Connects, But Syncing Fails or Stalls

This suggests the app cannot transfer data reliably.

Fix B1: Keep the App in Foreground During Sync

Mi Smart Band 4 sync can fail if the app is backgrounded mid-transfer.

Steps:

Open the app
Go to the band’s device page
Keep screen on until sync finishes
Avoid switching apps during the sync

Fix B2: Disable Battery Optimization for the Companion App

Android battery management is the most common reason syncing works only sometimes.

Steps:

Android Settings → Apps → (companion app)
Battery → set to Unrestricted or Not optimized
Allow background activity
If available, enable Autostart

Then try syncing again.

Fix B3: Check Permissions That Affect BLE and Sync

On many Android versions, BLE scanning and background behavior are tied to permissions.

Recommended permissions:

Nearby devices (newer Android)
Location (often required for BLE scanning)
Notifications (for alerts and sometimes background service stability)

Enable them, then retry sync.

Fix B4: Clear App Cache (Safe and Often Effective)

Steps:

Android Settings → Apps → (companion app) → Storage → Clear cache

Then open the app and sync again.

Symptom C: Sync Works Only When the App Is Open

This is almost always background restrictions.

Fix checklist:

Battery optimization disabled for the app
Background activity allowed
Background data allowed if Data Saver is used
Autostart enabled (if your phone supports it)
Keep the app locked in Recent Apps (some Android skins help keep it alive)

Once the app is allowed to run normally, the band will reconnect more consistently and sync in the background.

Symptom D: Band Appears in Android Bluetooth, But Not in the App

This happens when Android paired it directly, bypassing the companion app’s binding process.

Fix:

Android Settings → Bluetooth → Forget/Unpair the band
Open companion app → Add device / Pair band
Pair from inside the app only

The band’s full features depend on the app-based pairing, not a generic Bluetooth pairing.

Symptom E: The App Says the Band Is Already Paired or Bound to Another Account

Mi Smart Band 4 can be “bound” to an account. If it was previously connected elsewhere, pairing can fail.

Fix steps:

If you still have the old phone:
- Open the companion app on that phone
- Unpair/Remove the band properly
If you don’t have the old phone:
- Factory reset the band
- Then pair it again using your current phone and account

Factory reset is the last resort, but it’s often the cleanest fix for binding issues.

Connection Stability Improvements (Prevent Repeat Problems)

Keep Bluetooth Healthy

Avoid pairing too many Bluetooth wearables at once
Disconnect unused devices when troubleshooting
If you use Bluetooth earbuds constantly, try pairing the band first, then earbuds

Bluetooth radios are shared resources. Crowding can create random dropouts.

Keep Phone Time and Time Zone Automatic

Wrong time settings can cause odd sync behavior, including incorrect data timestamps.

Set:

Automatic date and time: On
Automatic time zone: On

Avoid Aggressive Battery Saver Modes

Battery saver modes can:

Restrict background scanning
Kill background services
Delay notifications
Interrupt sync

When troubleshooting, turn battery saver off temporarily.

Band-Side Troubleshooting

Restart the Band (Soft Reset)

If the band UI feels slow, stuck, or syncing is inconsistent:

Use the band’s restart option if available in Settings
If no restart option is visible, put it on the charger and reconnect firmly, then remove and try again

A reboot clears temporary glitches without deleting data.

Check Band Battery Level

Low battery can cause:

Weak Bluetooth stability
Failed sync attempts
Failed updates and partial transfers

Charge above 20–30% before troubleshooting. For firmware updates, aim for 50% or more.

App-Side Troubleshooting (When the App Is the Bottleneck)

Update the Companion App

Outdated apps can break pairing and syncing, especially after Android updates.

After updating:

Reopen the app
Sync again
Re-check permissions because Android updates can reset them

Sign Out and Sign In Again (Account Refresh)

If the app shows inconsistent device status:

Sign out of the companion app account
Sign back in
Go to device page and sync

This can refresh device binding and correct “stuck state” issues.

Clear App Data (Stronger Than Clearing Cache)

Only do this if nothing else works, because it resets app settings.

Steps:

Android Settings → Apps → (companion app) → Storage
Clear data
Reopen app, log in, pair the band again

Firmware and Update-Related Sync Failures

Symptom: Sync Fails After a Firmware Update Attempt

If the update partially applied, the band may behave oddly until resources complete syncing.

Fix steps:

Charge band above 50%
Open the app and keep it in foreground
Allow it to finish any pending update/resource transfer
Avoid switching apps until complete

If it still fails:

Unpair and re-pair in the companion app
Retry update afterward

Symptom: Band Reboots or Freezes During Sync

This can happen due to:

Corrupt resource file transfer
Unstable Bluetooth
App interruptions

Fix:

Restart phone
Clear app cache
Sync again in a quiet environment with minimal Bluetooth devices connected
If repeated, unpair and re-pair

The Clean Re-Pair Method (Most Effective “Reset Without Panic”)

If you’ve tried the basics and sync is still failing, clean re-pairing often fixes persistent issues without going straight to factory reset.

Steps:

In the companion app: Unpair/Remove the band
In Android Bluetooth settings: Forget/Unpair the band if it appears
Restart the phone
Open the companion app and pair the band again from inside the app
Sync and test with a short activity or a manual sync

This clears mismatched pairing records on both sides.

Factory Reset (Last Resort)

Use this only when:

The band is bound to another account and cannot be unpaired normally
Pairing code mismatches persist after clean re-pair
The band is stuck in a broken post-update state
Sync fails on multiple phones

General steps:

Band Settings → Factory reset → Confirm
Then:
Pair again through the companion app

Factory reset may erase local data on the band, so use it when you’ve exhausted non-destructive options.

Diagnostic Checklist: Pinpoint the Real Cause Quickly

If you want to identify the culprit without guessing, check these in order:

Does Bluetooth connect at all?
- If no: fix Bluetooth/ghost pairing/cache
Does it connect only when app is open?
- If yes: battery optimization/background restriction
Does syncing fail but connection stays stable?
- If yes: permissions/cache/app bug
Does pairing fail with “already paired/bound” messages?
- If yes: account binding/factory reset
Did it start after an update?
- If yes: complete pending resource transfer, then clean re-pair

Practical “Stable Everyday” Settings for Android

To keep Mi Smart Band 4 consistently connected and synced:

Battery for companion app: Unrestricted / Not optimized
Background activity: Allowed
Notifications: Allowed (also helps keep services alive)
Location/Nearby devices: Allowed
Bluetooth always on
Avoid frequent force-closing of the companion app
Sync once daily intentionally (open the app briefly), especially after heavy activity days

A stable Mi Smart Band 4 experience is mostly about giving the companion app permission to do its quiet work. Once Android stops “helpfully” shutting it down, the band behaves like a dependable extension of your phone rather than a device that needs daily coaxing.