To build Let’s Encrypt certificate your server needs to be contacted by the Let’s Encrypt public web servers in order to verify that you are the owner of the domain.
This means the Let’s Encrypt certificate cannot to be used on internal servers.
This Article is for Artica v4.50 with latest Hotfix or Service pack 1
“Your System” > “Certificate Center”
Creating an SSL certificate requires the use of the Reverse-proxy service. It is not installed on your server.
", please refer to this article