Android : Cannot send push notification via Azure Mobile Service

I have setup a Mobile Service in Azure and connected it to my Android app. Through this app I am calling the Azure API to insert an object into a database table linked to the mobile service.

I have written the script that is executed before it gets inserted. That script is intended to send a push notification to another device.

Now the case is, the object gets inserted into table but no push notification is received. What could be wrong? How can i debug?

Here's my insert script:

function insert(message, user, request) {

//This is logic to get receiver device's handler
var receiverHandle;

var deviceTable = tables.getTable('devices');
deviceTable.where({
    userId: item.receiver
}).read({
    success: fillHandle
});


request.execute({
    success: function() {
        // Write to the response and then send the notification in the background
        request.respond();
        push.gcm.send(item.handle, item.message, {
            success: function(response) {
                console.log('Push notification sent: ', response);
            }, error: function(error) {
                console.log('Error sending push notification: ', error);
            }
        });
    }
});

function fillHandle(results) {
    receiverHandle = results[0].handle;
}


request.execute({
        success: function() {
            // Write to the response and then send the notification in the background
            request.respond();
            push.gcm.send(receiverHandle, "Hello! Push", {
                success: function(response) {
                    console.log('Push notification sent: ', response);
                }, error: function(error) {
                    console.log('Error sending push notification: ', error);
                }
            });
        }
    });

}