Flutter workmanager error Area=BGTaskSchedulerErrorDomain Code=3 “(null)” on iOS

i am making an attempt to make use of workermanger with flutter about background service on ios.
So that is my plist

Now that is my AppDelegate on xcode:

 import UIKit
import Flutter
import workmanager


    @UIApplicationMain
    @objc class AppDelegate: FlutterAppDelegate {
        
    override func userNotificationCenter(_ middle: UNUserNotificationCenter,
                                            willPresent notification: UNNotification,
                                            withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
            completionHandler(.alert) // exhibits banner even when app is in foreground
        }
        
    
        override func software(_ software: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
            WorkmanagerPlugin.registerTask(withIdentifier: "simpleTask")
            UIApplication.shared.setMinimumBackgroundFetchInterval(TimeInterval(60*15))
            GeneratedPluginRegistrant.register(with: self)
            return tremendous.software(software, didFinishLaunchingWithOptions: launchOptions)
        }
    }

and now that is my Flutter code

import 'package deal:workmanager/workmanager.dart';

@pragma('vm:entry-point')
void callbackDispatcher() {
  Workmanager().executeTask((process, inputData) {
    change (process) {
      case Workmanager.iOSBackgroundTask:
        print("The iOS background fetch was triggered");
        break;
    }
    bool success = true;
    return Future.worth(success);
  });
}
void predominant() {
    WidgetsFlutterBinding.ensureInitialized();
   Workmanager().initialize(
    callbackDispatcher, // The highest degree perform, aka callbackDispatcher
    isInDebugMode: true // If enabled it should put up a notification at any time when the duty is operating. Helpful for debugging duties
  );
  Workmanager().registerOneOffTask("simpleTask", "simpleTask");
  // Workmanager().registerPeriodicTask("simpleTask", "simpleTask");
  runApp(const MyApp());  
}

The error i obtain is that this:

Couldn't schedule app refresh: Error Area=BGTaskSchedulerErrorDomain Code=3 "(null)"

are you able to recommend me the place i am misplaced? Perhaps in regards to the documentation, i can not perceive i ask assist to you.