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....