plgVmOnPaymentNotification is not triggering for my plugin

[njpong]

Hi All,
I am currently developing a VirtueMart payment plugin for my company's payment gateway.
For the plugin , I am facing issue for the callback section which is using the plgVmOnPaymentNotification.

As I am working on the localhost using UWamp, so I am using ngrok to receive the response sent by the payment gateway.
The sample notification url used by me is as follow:
"notification_url" => "https://xxxxx.ngrok.io/VirtueMart/" .'index.php?option=com_virtuemart&view=vmplg&task=pluginNotification&tmpl=component&on=' . $order['details']['BT']->order_number . '&pm=' . $order['details']['BT']->virtuemart_paymentmethod_id . "&o_id={$order['details']['BT']->virtuemart_order_id}"

I have found out that only the Paypal plgVmOnPaymentNotification is triggering by the POST data.
plgVmOnPaymentNotification on my plugin does not get trigger at all.
Therefore the POST data sent by the payment gateway will never reach my plugin's plgVmOnPaymentNotification.
Thus the callback for order status change will never work.
I need some advice on callback for the order.
Any help will be appreciated , thanks!

Joomla version : 3.6.2
VirtueMart version : 3.0.18
PHP : 5.6.18

[Studio 42]

Have you added the function plgVmOnPaymentNotification in your plugin ?