We are also getting this issue when trying to test integration in our ASP.NET MVC project. We have generated our certificate and verified the merchant domain and get the Merchant Identifier back from the certificate ok but when making the request to https://apple-pay-gateway-cert.apple.com/paymentservices/startSession we get this error: "An existing connection was forcibly closed by the remote host" or "The request was aborted: Could not create SSL/TLS secure channel." Do Apple not have any working examples of successfully integrating with Apple Pay from an ASP.Net website? The only thing I can find is from third parties such as Just Eat.