Hosted Pay Page (Data Preload) response is blank (PHP)

UPDATE: Not sure if this documented anywhere, but the curl when applied to an existing store (a store existing before Data Preload feature was added) does NOT work. If you create a new store from scratch, the curl does work. It appears that stores existing before the feature do not work, and one would need to create a new one. Can Moneris confirm this behaviour?
 
 
Testing the PHP script (over https) below but always getting empty response. When I make a change to the $url I get data back pertaining it failing to connect, and when I change store ID or store KEY, I also get notices pertaining invalid credentials, meaning that it is getting data back.

I am not able to get any response back, no matter what I have tried. Should be straight forward, but nothing is getting back.
 
running this on the command line:
 
curl -d "ps_store_id=xxxxx&hpp_key=yyyyy&charge_total=100.00&order_id=12343567&hpp_preload=" -X POST https://esqa.moneris.com/HPPDP/index.php
 
also yields nothing
 
Does one need to enable anything in the admin configuration of the test store?

I looked at the config and read the doc, but I could not see any reference to such.

Tried the same on the prod server, and getting the same results.

I am located in Canada. Thank you.



----------------------------------------------------- PHP TEST CODE BELOW -----------------------------------------------------
 
<?php

$url = "https://esqa.moneris.com/HPPDP/index.php";
$store_id = "xxxxx"; 
$hpp_key = "yyyyy"; 
 
$charge_total = "100.00";

$dataToSend = "ps_store_id=$store_id&hpp_key=$hpp_key&charge_total=$charge_total&hpp_preload=";

 
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $dataToSend);
curl_setopt($ch, CURLOPT_TIMEOUT, $gArray['CLIENT_TIMEOUT']);
curl_setopt($ch, CURLOPT_USERAGENT, $gArray['API_VERSION']);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
 
$httpCode = curl_getinfo($ch , CURLINFO_HTTP_CODE); 

$response = curl_exec($ch);
 
echo "Response : " . $response . "<br/>";
 
?>