PKCS#7 certificate with Httpclient in C#

Question

I'm trying to read a PKCS#7 certificate with Httpclient. But getting error.

var certPath = HostingEnvironment.MapPath(@"~/Certificates/", certName);
var certCollection = new X509Certificate2Collection();
certCollection.Import(certPath);
var handler = new WebRequestHandler();
handler.ClientCertificates.AddRange(certCollection);
var client = new HttpClient(handler);
var result = await client.SendAsync(url, requestMessage);

Error: WebException: The request was aborted: Could not create SSL/TLS Secure channel.