The SSL connection could not be established, see inner exception.

Common causes

• The server certificate is untrusted, expired or for another name (inner: "The remote certificate is invalid...").
• No TLS version or cipher in common with the server.
• The connection was closed during the handshake by a proxy or firewall (inner: "Received an unexpected EOF or 0 bytes from the transport stream").

How to fix it

1. Log the full exception including InnerException to see the real cause.
2. On Linux containers, install and update ca-certificates.
3. Check the certificate and TLS versions the server offers.
4. Returning true from ServerCertificateCustomValidationCallback hides the problem and is not a fix.