Im integrating eSignature API using ASP .NET web api core and getting the below error after deploying it on our test site.  My test server supports TLS12 and I explicitly set it for http client handler in my api for DocusignClient.  

Monitored the traffic using Wireshark and I could see my test server sends hello handshake, but I do not see the hello handshake from Docusign server, 

Any leads to resolve this issue greatly appreciated. Thank you

Error Content: System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.
 ---> 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 (10054): An existing connection was forcibly closed by the remote host.
   --- End of inner exception stack trace ---