dfu device not connected

[ManikandanRajamanickam12]

refresh() - device: xxxxxxxxx
I/DfuBaseService( 9486): Refreshing result: true
I/DfuBaseService( 9486): Cleaning up...
D/BluetoothGatt( 9486): cancelOpen() - device: xxxxxxxxxx
D/BluetoothGatt( 9486): close()
D/BluetoothGatt( 9486): unregisterApp() - mClientIf=8
I/DfuBaseService( 9486): Restarting the service
I/DfuBaseService( 9486): Starting DFU service in foreground
I/DfuBaseService( 9486): Connecting to the device...
D/BluetoothGatt( 9486): connect() - device: xxxxxxxx, auto: false
D/BluetoothGatt( 9486): registerApp()
D/BluetoothGatt( 9486): registerApp() - UUID=xxxxxxxxx
D/BluetoothGatt( 9486): onClientRegistered() - status=0 clientIf=8
D/BluetoothGatt( 9486): onClientConnectionState() - status=133 clientIf=8 device=xxxxxxxxxx
E/DfuBaseService( 9486): Connection state change error: 133 newState: 0
I/DfuBaseService( 9486): Connection error after: 30008 ms
E/DfuBaseService( 9486): Device not reachable. Check if the device with address xxxxxxxxx is in range, is advertising and is connectable
I/DfuBaseService( 9486): Attempt: 3
D/BluetoothGatt( 9486): refresh() - device: xxxxxxxx
I/DfuBaseService( 9486): Refreshing result: true
I/DfuBaseService( 9486): Cleaning up...
D/BluetoothGatt( 9486): cancelOpen() - device:xxxxxxxx
D/BluetoothGatt( 9486): close()
D/BluetoothGatt( 9486): unregisterApp() - mClientIf=8
I/DfuBaseService( 9486): DFU service destroyed
I/flutter ( 9486): PlatformException(133, DFU FAILED: GATT ERROR, Address: xxxxxxxxxxx, Error Type: 1, null)

I am facing this problem while upgrade a firmware.can any one help me to solve this problem....