Verify that your notification content length,content type and headers are correct.
For Tile notifications you need the following headers :
sendNotificationRequest.Headers.Add("X-WindowsPhone-Target", "token");
sendNotificationRequest.Headers.Add("X-NotificationClass", "1");
and before headers, set the content length and type as follows :
sendNotificationRequest.ContentLength = notificationMessage.Length;
sendNotificationRequest.ContentType = "text/xml";
If you don't specify the headers correctly that can make Notification Status as Suppressed. This might be useful.