The request was aborted: Could not create SSL/TLS secure channel

I am testing the moneris gateway payment, by using the testing site for CA.

https://esqa.moneris.com/mpg/

Coding is in asp.net C#, with .Net 4.5.1

Just trying a simple purchase from online,  but it returns error below:

CardType: null;TransAmount: null;TxnNumber: null;ReceiptId: Global Error Receipt;TransType: null;ReferenceNum: null;ResponseCode: null;ISO: null;BankTotals: ;Message: The request was aborted: Could not create SSL/TLS secure channel.;AuthCode: null;Complete: false;TransDate: null;TransTime: null;Ticket: ;TimedOut: null;IsVisaDebit: ;

Coding is as below:

public string Paying(string stdid)
{

string sresult = "";
string order_id = "AC" + DateTime.Now.ToString("yyyyMMddhhmmss");
string store_id = "store5";
string api_token = "yesguy";
string amount = "7.00";
string pan = "4242424242424242";
string expdate = "1901"; //YYMM format
string crypt = "7";
string processing_country_code = "CA";
bool status_check = false;

Purchase purchase = new Purchase();
purchase.SetOrderId(order_id);
purchase.SetAmount(amount);
purchase.SetPan(pan);
purchase.SetExpDate(expdate);
purchase.SetCryptType(crypt);
purchase.SetDynamicDescriptor("Simple payment");

HttpsPostRequest mpgReq = new HttpsPostRequest();
mpgReq.SetProcCountryCode(processing_country_code);
mpgReq.SetTestMode(true); //false or comment out this line for production transactions
mpgReq.SetStoreId(store_id);
mpgReq.SetApiToken(api_token);
mpgReq.SetTransaction(purchase);
mpgReq.SetStatusCheck(status_check);
mpgReq.Send();

try
{
Moneris.Receipt receipt = mpgReq.GetReceipt();
sresult = "CardType: " + receipt.GetCardType() + ";";
sresult += "TransAmount: " + receipt.GetTransAmount() + ";";
sresult += "TxnNumber: " + receipt.GetTxnNumber() + ";";
sresult += "ReceiptId: " + receipt.GetReceiptId() + ";";
sresult += "TransType: " + receipt.GetTransType() + ";";
sresult += "ReferenceNum: " + receipt.GetReferenceNum() + ";";
sresult += "ResponseCode: " + receipt.GetResponseCode() + ";";
sresult += "ISO: " + receipt.GetISO() + ";";

sresult += "BankTotals: " + receipt.GetBankTotals() + ";";
sresult += "Message: " + receipt.GetMessage() + ";";
sresult += "AuthCode: " + receipt.GetAuthCode() + ";";
sresult += "Complete: " + receipt.GetComplete() + ";";
sresult += "TransDate: " + receipt.GetTransDate() + ";";

sresult += "TransTime: " + receipt.GetTransTime() + ";";
sresult += "Ticket: " + receipt.GetTicket() + ";";
sresult += "TimedOut: " + receipt.GetTimedOut() + ";";
sresult += "IsVisaDebit: " + receipt.GetIsVisaDebit() + ";";

sresult = sresult;

}
catch (Exception e)
{

sresult =  e.Message ;
}


return sresult;
}

 

I searched and tried around, but still no luck. 

 

Can anyone help?  

 

Thanks.