My App nothing stopped working.

My App nothing stopped working. I was writing code for Notifications. I did not put, only comment/uncomment code. Before was working and nothin stpped working. My MainActivity:

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;

using Android.Gms.Common;
using Firebase.Messaging;
using Firebase.Iid;
using Android.Util;
using PushNotification.Plugin;
using Newtonsoft.Json.Linq;
using PushNotification.Plugin.Abstractions;
using Android.Content;
using Java.Lang;

namespace Autorizador.Droid
{
    [Activity(Label = "Autorizador", Icon = "@drawable/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : //global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
         global::Xamarin.Forms.Platform.Android.FormsApplicationActivity
    {
        public static Context AppContext;
        protected override void OnCreate(Bundle bundle)
        {
            //TabLayoutResource = Resource.Layout.Tabbar;
            //ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(bundle);

            global::Xamarin.Forms.Forms.Init(this, bundle);

            //AppContext = this.ApplicationContext;

            //CrossPushNotification.Initialize<CrossPushNotificationListener>("840100012845");

            //StartPushService();

            LoadApplication(new App());
        }

        public static void StartPushService()
        {
            AppContext.StartService(new Intent(AppContext, typeof(PushNotificationService)));

            if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.Kitkat)
            {

                PendingIntent pintent = PendingIntent.GetService(AppContext, 0, new Intent(AppContext, typeof(PushNotificationService)), 0);
                AlarmManager alarm = (AlarmManager)AppContext.GetSystemService(Context.AlarmService);
                alarm.Cancel(pintent);
            }
        }

        public static void StopPushService()
        {
            AppContext.StopService(new Intent(AppContext, typeof(PushNotificationService)));
            if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.Kitkat)
            {
                PendingIntent pintent = PendingIntent.GetService(AppContext, 0, new Intent(AppContext, typeof(PushNotificationService)), 0);
                AlarmManager alarm = (AlarmManager)AppContext.GetSystemService(Context.AlarmService);
                alarm.Cancel(pintent);
            }
        }
    }
}

My App.xaml.cs

using PushNotification.Plugin;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Xamarin.Forms;
using System.Threading.Tasks;
using System.Threading;
using System.Diagnostics;

namespace Autorizador
{
    public partial class App : Application
    {
        public static CancellationTokenSource CancellationToken { get; set; }
        private Label _label = new Label();
        public App()
        {
            InitializeComponent();

            //MainPage = new Autorizador.MainPage();
            MainPage = new NavigationPage(new Autorizador.MainPage());
        }


        protected override void OnStart()
        {
            //CrossPushNotification.Current.Unregister();
            //CrossPushNotification.Current.Register();
        }

        protected override void OnSleep()
        {
            // Handle when your app sleeps
        }

        protected override void OnResume()
        {
            // Handle when your app resumes
        }
    }
}