The error message, "Could not establish a trust relationship for the SSL/TLS secure channel," specifically indicates a certificate validation failure. This occurs during the TLS handshake when the client (Session Recording Agent) attempts to connect to the server (Session Recording Server). The client must be able to validate the server's certificate against a trusted Certificate Authority (CA). If the CA that signed the server's certificate is not trusted by the machine hosting the Agent, or if the necessary CA certificate is missing from the Agent's trust store, this error will be generated, and the connection will fail.

A. A server being down or unavailable would typically result in a connection timeout or "connection refused" error, not a specific SSL/TLS trust relationship failure.

B. Policy evaluation occurs after a secure connection between the Agent and Server has already been successfully established. This error prevents that initial connection.

1. Citrix Virtual Apps and Desktops Product Documentation, Session Recording > Troubleshoot > Agent cannot connect to server: The troubleshooting guide addresses connectivity issues. It states, "If you use HTTPS, verify that a valid server certificate is on the Session Recording server and the CA certificate is on the VDA." This directly supports that a missing or untrusted CA certificate on the VDA (hosting the Agent) causes connection failure.

Source: Citrix Virtual Apps and Desktops 7 2203 LTSR, Product Documentation, "Troubleshoot Session Recording".

2. Citrix Virtual Apps and Desktops Product Documentation, Session Recording > Install > Step 3. Install the Session Recording Server: This section details the prerequisites and configuration for the server, including communication protocols. It specifies, "For the HTTPS protocol, you must bind a certificate to the site in IIS." It implicitly requires that clients connecting to this HTTPS site (i.e., the Session Recording Agents) must trust this certificate.

Source: Citrix Virtual Apps and Desktops 7 2203 LTSR, Product Documentation, "Install Session Recording".

3. Microsoft .NET Framework Documentation, System.Net.WebExceptionStatus Enum: The error message is a standard .NET exception. The underlying WebExceptionStatus is TrustFailure. Microsoft's documentation describes this status as: "A server certificate could not be validated." This confirms the issue is rooted in certificate validation, aligning with options C and D.

Source: Microsoft Docs, ".NET API browser", System.Net.WebExceptionStatus.