The request was aborted: Could not create SSL/TLS secure channel

Question

We are unable to connect to an HTTPS server using WebRequest because of this error message:

The request was aborted: Could not create SSL/TLS secur

Answer 1

The error is generic and there are many reasons why the SSL/TLS negotiation may fail. The most common is an invalid or expired server certificate, and you took care of that by providing your own server certificate validation hook, but is not necessarily the only reason. The server may require mutual authentication, it may be configured with a suites of ciphers not supported by your client, it may have a time drift too big for the handshake to succeed and many more reasons.

The best solution is to use the SChannel troubleshooting tools set. SChannel is the SSPI provider responsible for SSL and TLS and your client will use it for the handshake. Take a look at TLS/SSL Tools and Settings.

Also see How to enable Schannel event logging.