Notification aus Backgroundtask sendet nicht korrekt!

public class OfflineUpdate extends IntentService{
    public OfflineUpdate() {
        super("OfflineUpdater");
    }


    @Override
    protected void onHandleIntent(@Nullable Intent intent) {
        NotificationUtils.sendNotification(this,"Update", "Hello hello!");
        Toast.makeText(this,"UpdateGlobal",Toast.LENGTH_SHORT).show();


        ListManager.update(this);


    }
}


//Notification Utils
public class NotificationUtils {
    public static void sendNotification(Context c, String title, String message) {
        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(c)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentTitle(title)
                .setContentText(message);
        Intent resultIntent = new Intent(c, MainActivity.class);




        TaskStackBuilder stackBuilder = TaskStackBuilder.create(c);
        stackBuilder.addParentStack(MainActivity.class);
        stackBuilder.addNextIntent(resultIntent);
        PendingIntent resultPendingIntent = stackBuilder.getPendingIntent(0,
                PendingIntent.FLAG_UPDATE_CURRENT);
        mBuilder.setContentIntent(resultPendingIntent);
        NotificationManager mNotificationManager =
                (NotificationManager) c.getSystemService(Context.NOTIFICATION_SERVICE);
        mNotificationManager.notify(1, mBuilder.build());
    }
}