title: InvalidRegistration in FCM pushnotification
body: <p>I am Trying to use FCM for push Notification But I get a Error</p>
  
  <blockquote>
    <p>{"multicast_id":5438269995043250343,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]}</p>
  </blockquote>
  
  <p>My Code is:</p>
  
  <pre><code>var applicationID = "AAAAU1NcEvw:APA91bF6V....blq3lFdU";
              var senderId = "357...668";
              string deviceId = "cmWVx1UBniA:APA91b.....ukG77K";
              WebRequest tRequest = WebRequest.Create("https://fcm.googleapis.com/fcm/send");
              tRequest.Method = "post";
              tRequest.ContentType = "application/json";
              var data = new
              {
                  to = deviceId,
                  notification = new
                  {
                      body = "This is the message",
                      title = "This is the title",
                      icon = "myicon"
                  }
              };
              var json = jss.Serialize(data);
              Byte[] byteArray = Encoding.UTF8.GetBytes(json);
              tRequest.Headers.Add(string.Format("Authorization: key={0}", applicationID));
              tRequest.Headers.Add(string.Format("Sender: id={0}", senderId));
              tRequest.ContentLength = byteArray.Length;
  
              using (Stream dataStream = tRequest.GetRequestStream())
              {
                  dataStream.Write(byteArray, 0, byteArray.Length);
                  using (WebResponse tResponse = tRequest.GetResponse())
                  {
                      using (Stream dataStreamResponse = tResponse.GetResponseStream())
                      using (StreamReader tReader = new StreamReader(dataStreamResponse))
                      {
                          String sResponseFromServer = tReader.ReadToEnd();
                          // Response.Write(sResponseFromServer);
                      }
                  }
              }
  </code></pre>