System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send

Solucion - forzar TLS 1.2

 var securityProtocol = (int)System.Net.ServicePointManager.SecurityProtocol;

                // 0 = SystemDefault in .NET 4.7+

                if (securityProtocol != 0)

                {

                    Log.Info(securityProtocol);

                    System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12;

                    Log.Info("allocated Security Protocal: " + ServicePointManager.SecurityProtocol);

                }

System.AggregateException: One or more errors occurred. ---> System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

   at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)

   at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)

   --- End of inner exception stack trace ---

   at System.Net.TlsStream.EndWrite(IAsyncResult asyncResult)

   at System.Net.PooledStream.EndWrite(IAsyncResult asyncResult)

   at System.Net.ConnectStream.WriteHeadersCallback(IAsyncResult ar)

   --- End of inner exception stack trace ---

   at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)

   at System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResult ar)

   --- End of inner exception stack trace ---

   --- End of inner exception stack trace ---

   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)

   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)

   at System.Threading.Tasks.Task`1.get_Result()

System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

   at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)

   at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)

   --- End of inner exception stack trace ---

   at System.Net.TlsStream.EndWrite(IAsyncResult asyncResult)

   at System.Net.PooledStream.EndWrite(IAsyncResult asyncResult)

   at System.Net.ConnectStream.WriteHeadersCallback(IAsyncResult ar)

   --- End of inner exception stack trace ---

   at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)

   at System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResult ar)

   --- End of inner exception stack trace ---<---