Push Notifications not working using GCM - google-cloud-messaging

Question

We have a android application development in progress, where in we are supposed to go for Topic Messaging using GCM (C#).
We have Created Entries in Google Developer Console to enable Cloud Messaging for our Android App and have got API Key + Sender ID + Server Key + Browser Key.
We have written the Server Side Implementation in a console Application/ASMX Web Service to check the Push using API Key/Browser Key + Sender ID + Topic name and we have been successful in getting the MessageID/Multicast ID from GCM.
At Client End, we have handled as per the documentation provided at xamarin for Android and placed Listener Services (Registration, Intent, GCM ) properly by using SenderID + Topicname. We are getting Registration Token and have subscribed to a topic as well as documented.
But we are currently not getting push notification at the client end. Is it something which we have missed in the implementation part? Kindly Suggest.
Android Manifest File:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.xamarin.gcmexample" android:versionCode="1" android:versionName="1.0">
<uses-sdk />
<application android:label="Notifications" android:icon="#drawable/Icon"></application>
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="com.xamarin.gcmexample.permission.C2D_MESSAGE" />
<permission android:name="com.xamarin.gcmexample.permission.C2D_MESSAGE" android:protectionLevel="signature" />
<application android:label="Notifications" android:icon="#drawable/Icon">
<receiver android:name="com.google.android.gms.gcm.GcmReceiver" android:exported="true" android:permission="com.google.android.c2dm.permission.SEND">
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
<action android:name="com.google.android.c2dm.intent.REGISTRATION" />
<category android:name="com.xamarin.gcmexample" />
</intent-filter>
</receiver>
<service android:name="com.example.MyGcmListenerService" android:exported="false">
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
</intent-filter>
</service>
<service android:name="com.example.MyInstanceIDListenerService" android:exported="false">
<intent-filter>
<action android:name="com.google.android.gms.iid.InstanceID" />
</intent-filter>
</service>
</application>
</manifest>
GCMReceiver Code
[Service(Exported = false), IntentFilter(new[] { "com.google.android.c2dm.intent.RECEIVE" })]
public class MyGcmListenerService : GcmListenerService
{
public override void OnMessageReceived(string from, Bundle data)
{
var message = data.GetString("message");
Log.Debug("MyGcmListenerService", "From: " + from);
Log.Debug("MyGcmListenerService", "Message: " + message);
SendNotification(message);
}
void SendNotification(string message)
{
var intent = new Intent(this, typeof(MainActivity));
intent.AddFlags(ActivityFlags.ClearTop);
var pendingIntent = PendingIntent.GetActivity(this, 0, intent, PendingIntentFlags.OneShot);
var notificationBuilder = new Notification.Builder(this)
.SetSmallIcon(Resource.Drawable.Icon)
.SetContentTitle("GCM Message")
.SetContentText(message)
.SetAutoCancel(true)
.SetContentIntent(pendingIntent);
var notificationManager = (NotificationManager)GetSystemService(Context.NotificationService);
notificationManager.Notify(0, notificationBuilder.Build());
}
}