Ensure the "Safeguard Appliance DNS Name or IP Address" entered into the collector agent matches the SSL web certificate of Safeguard.
Ensure, the certificate which signed the Safeguard SSL web certificate is installed onto the Windows machines running the collector,. This is done by adding the certificate into the Certificate stored on windows. (Typically, the Local Machine -> Trusted Root Certificate Authorities. )
Trust can be validated, by connecting to Safeguard using a browser on the Collector machine, and going to HTTPS:// IP or DNS name (as entered in "Safeguard Appliance DNS Name or IP Address")