Geocortex Essentials Install "Could not establish trust relationship"

I am trying to install Geocortex Essentials 4.14.5 (although i tried previous version with the same results).

I can install the software but when it goes to do the post installation configuration the connection times out.  Using the Log Viewer utility i can see that there are multiple errors

"Error performing Elastic Search operation https://<myserver>:19201/_nodes... Could not establish trust relationship for the SSL/TLS secure channel"

Do i have to bind an ssl cert to port 19201 ?I have installed this software multiple times on different servers and have never had to configure any of the ports before.

Any idea what might be causing this ?

Thanks,

Rob