The underlying connection was closed within C# dll from VB6

Question

I have done a C# dll and I'm using it from an old VB6 project.

I can correctly use it, but I have a problem.

In this dll, I make an http request to a server of mine, where I have set a wcf service. This code works well when I try to execute it from C#, but in VB6 it gives me the error System.Net.WebException: The underlying connection was closed: The connection was closed unexpectedly.

I have already done what you can see here and this is my http request code:

 private bool HTTPSgetRequest(string url, out string detail)  
        {
            var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
            httpWebRequest.ContentType = "text/json";
            httpWebRequest.KeepAlive = false;
            Uri myUri = new Uri(url);
            httpWebRequest.Method = "GET";
            try
            {
                var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
                using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
                {
                    detail = streamReader.ReadToEnd();
                }
                if (httpResponse.StatusCode == HttpStatusCode.OK)
                    return true;
            }
            catch (Exception e)
            {
                detail = e.ToString();
            }
            return false;
        }

So, I've added the keepAlive = false, but nothing changed, it still goes in the cath branch. Why? And what can I do now?