I have implemented Let's Encrypt on a COS Home with mybox.poweredbyclear.com and it works fine. What I would like to do is to add a few subdomains to this but am having no luck. There is not option to add to exiting Lets Encrypt cert from webconfigure. If I try the --expand from cerbot then I get "cerbot does not know how to configure the web server". What am I missing here? Do I need to register a domain to do this? I STW and found several suggestions but am reluctant to implement them as that I don't want to break anything.