SSL connection issue while logging into elastic search server

[Phani_Sekhar_Veesam]

We are trying post the logs in Elasticsearch, but getting the below error from .net core. please guide me how to solve this error.

using (var handler = new HttpClientHandler())
{

                    handler.SslProtocols = SslProtocols.Tls12 | SslProtocols.Tls11 | SslProtocols.Tls;

                    X509Certificate2 certificate1 = new X509Certificate2(@"path/certifi.cer");

                    handler.ClientCertificates.Add(certificate1);

                    using (var client = new HttpClient(handler))
                    {
                        client.DefaultRequestHeaders.Accept.Clear();
                        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

                        jsonstr = JsonConvert.SerializeObject(cur);

                        var content = new StringContent(jsonstr, Encoding.UTF8, "application/json");

                        var response = await client.PostAsync(LogServer, content);

                        res = await response.Content.ReadAsStringAsync();
                        if (res != "OK")
                        {
                            throw new Exception("Send to log server failed: res:" + res);
                        }
                    }
                }