Isolate play stop audio sound flutter not working

hi i want to implement an Isolate to play stop audio ringtone from assets
i have created isolate but don’t know why it is not working is anybody have any idea what i am missing here below is my sample code

void audioIsolateEntry() async {
   final ReceivePort receivePort = ReceivePort();
     IsolateNameServer.registerPortWithName(receivePort.sendPort, 'audio_isolate');

 final audioPlayer = AudioPlayer();

receivePort.listen((message) async {
  if (message == 'play') {
     debugPrint('Playing audio...');
    await audioPlayer.setSource(AssetSource('ringtone.mp3'));
  await audioPlayer.resume();
  } else if (message == 'pause') {
   debugPrint('Pausing audio...');
  await audioPlayer.pause();
} else if (message == 'stop') {
  debugPrint('Stopping audio...');
  await audioPlayer.stop();
  }
 });
 }

void main() async {
    WidgetsFlutterBinding.ensureInitialized();
   runApp(const MyApp());
  }

   void playAudio() {
     final isolate = IsolateNameServer.lookupPortByName('audio_isolate');
     debugPrint('play isolate $isolate');
  if (isolate != null) {
   debugPrint('playing $isolate');

    isolate.send('play');
   } else {
   debugPrint('Isolate not found!');
  }
  }

 void pauseAudio() async {
  final isolate = await IsolateNameServer.lookupPortByName('audio_isolate');
   if (isolate != null) {
    isolate.send('pause');
 } else {
   debugPrint('Isolate not found!');
}
}

void stopAudio() async {
  final isolate = await IsolateNameServer.lookupPortByName('audio_isolate');
if (isolate != null) {
isolate.send('stop');
 } else {
debugPrint('Isolate not found!');
 }

}

  class MyApp extends StatefulWidget {
    const MyApp({super.key});

 @override
 State<MyApp> createState() => _MyAppState();
  }

  class _MyAppState extends State<MyApp> {
     AudioPlayer? audioPlayer;
    @override
    void initState() {
      super.initState();

      register();
   }



 @override
 Widget build(BuildContext context) {
    return MaterialApp(
     home: Scaffold(
    appBar: AppBar(
      title: const Text('Audio Player'),
    ),
    body: Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children:[
          ElevatedButton(
            onPressed: () async {
              playAudio();
            },
            child: const Text('Play'),
          ),
          ElevatedButton(
            onPressed: () {
              stopAudio();
            },
            child: const Text('Stop'),
          ),
        ],
      ),
    ),
  ),
);
 }

void register() {
  audioIsolateEntry();
}
  }