How tridium certificate works?

I have a site with multiple Jace. It happened couple times, I have to reapprove server host from Jace to make connection works. The certificate is for 2 years, why it failed and need to manually reapprove?

Tim, do you have a tridium account setup. Recent Tridium talk had some good topic about Certificate and best practice.

yes i do. tridium talk refers to tridium university?