Last I was told, there is no cPanel plugin for Lets Encrypt, only a WHM plugin. There's a major difference. A WHM plugin is managed by root admins, and is global to everybody on the server. The WHM plugin issues a certificate for every single account and domain on the server. It has a stupidly low limit of I believe 20 certs a week that we'd go over in a single day...we have way too many new accounts per day for it. In addition, SSL adds extra load to our (and LE's, for issuing the certs) servers, and many domains hosted here probably wouldn't use SSL even if we made it standard on all accounts. As of right now, due to the lack of available software and LE's restrictions, there is no way for normal users to properly automate Lets Encrypt on our service. You can however manually generate a certificate for your domain every 90 days and install it. See this guide for that: http://wiki.helionet.org/Installing_an_SSL_Certificate_with_ZeroSSL