Cannot Process Moneris Response

Hi,

Starting yesterday, our clients were being charged via HPP (data preload), but the response from Moneris was redirecting the user back to the login page. This means that we were not updating the client's balance in our system even though they paid. This was not happening for the last 2.5 years.

After trying in vain to trace what was going on I just discovered that this is happening on Chrome, FireFox and IE11 but seems to be fine in Edge.

The application was developed using .Net. Here is the page_load event of the page that is supposed to process the response from Moneris:

        protected void Page_Load(object sender, EventArgs e) {
            WebLog("PaymentApproved: Called by Moneris", "");
            try {
                if (Session["PP"].ToString() == "PP") {
                    Session["PP"] = "";
                    if (!IsPostBack) {
                        WebLog("PaymentApproved: Handling Moneris Response", "");
                        ProcessMonerisResponse();
                    }
                } else {
                    Response.Redirect("Default.aspx");
                }
            } catch (Exception m) {
                WebLog("PaymentApproved: Page_Load Error!", "Payment approved but Multiplan not updated. " + m.Message);
            }
        }

It never gets to the first WebLog call! When inspecting the network traffic, you can see that it hits the PaymentApproved page, then it immediately redirects to the Login page.

It's driving me nuts. Is it a Certificate issue? Why is it only working in Edge? Why did it stop working now after a couple years?

Please let me know if you think you have an answer, or if you need to see more details.

Thanks,

Elie