Flutter BluetoothPort connection device is lost

Question

I tried to print pdf from Flutter app in Zebra ZQ620 by bluetooth. But I get a problem, it seems that I lost Bluetooth port connection. I use Flutter Bluetooth_print package. In my print_page.dart

@override
void initState() {
    super.initState();
    WidgetsBinding.instance!.addPostFrameCallback((_) => {initPrinter()});
}

Future<void> initPrinter() async {
    bluetoothPrint.startScan(timeout: Duration(seconds: 3));

    if (!mounted) return;
    bluetoothPrint.scanResults.listen(
       (val) {
           if (!mounted) return;
           setState(() => {_devices = val});
           if (_devices.isEmpty)
           setState(() {
                _devicesMsg = "No Devices";
           });
       },
    );
}

I successfully retrieve devices printer list. But when I tried to print, I lost connection. So please, I need help to fix it or if someone could give me an advice about another Flutter's package. I have to run into Ipad. I already tried with esc_pos_bluetooth and blue_print but it's just Bluetooth_print that seems to be what I need. Thank's !