The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.

The download error Could not establish trust relationship for the SSL/TLS secure channel. is generally related to your machine not trusting the website’s root Certificate Authority. We are generally pretty limited in the amount of support we can provide for issues related to web filters, firewalls, proxies, certificate trust, or other network-related errors. However, our resolution below will generally help diagnose and resolve this specific error. 

Topics covered in this article:

Determine if You are Affected

If affected, you will see an error similar to below in one of the following log files PatchMyPC.log or SMS_ISVUPDATES_SYNCAGENT.log, dependent on the publishing method you are using.

WebClient report an error during download: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.
An error occurred while downloading the file: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. [System.AggregateException]

This error is usually because the Root Certificate authority issuing the SSL certificate is not trusted on your device.

Resolution: Validate the Web Sites SSL Certificate is Trusted

If affected, you will see the following error in one of the following log file PatchMyPC.log or SMS_ISVUPDATES_SYNCAGENT.log, dependent on the publishing method you are using.

Here’s an example of how the log would appear if SnagIt were failing to download.

Starting download for: https://download.techsmith.com/snagit/releases/1915/snagit.exe
WebClient report an error during download: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.
An error occurred while downloading the file: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. [System.AggregateException]

On the machine receiving the error, navigate to the URL from the log file for the download failing with this error.

A common reason you may receive the error Could not establish trust relationship for the SSL/TLS secure channel is because the SSL certificate isn’t trusted.

If the SSL certificate is not trusted, you will need to install the SSL certificate’s root certificate.

For more details about this process for many common published certificate authorities, please review this article SSL Certificate Not Trusted Error.