[delphi-en] XML response from HTTP request

[dinol.softedge]

I am trying to manage license for my product through the Plimus payment 
gateway.  I need to request an XML response from their server.  I have the 
following code so far

procedure TForm1.Button1Click(Sender: TObject);
var
  data: TIdMultiPartFormDataStream;
begin
  data := TIdMultiPartFormDataStream.Create;
  try
    { add the used parameters for the script }
    data.AddFormField('param1', 'value1');
    data.AddFormField('param2', 'value2');
    data.AddFormField('param3', 'value3');

    { Call the Post method of TIdHTTP and read the result into TMemo }
    Memo1.Lines.Text := 
IdHTTP1.Post('https://www.plimus.com/jsp/validateKey.jsp?action=REGISTER&productId=XXXXXXX&key=XXX-XXXX-XXXX-XXXX',
 data);
  finally
    data.Free;
  end;
end;

This type of post request works on a normal http request but not on https 
request.  Can anyone give me an idea what to do.  Thanks