Question
Why do I receive "The commonName argument is invalid" when running /usr/local/cpanel/bin/checkallsslcerts for the Hostname SSL?
Answer
When the Hostname of your server contains the common name of a domain such as Yahoo, Paypal, Amazon, Google, etc, you will want to change the Hostname to a fully qualified domain name using a domain you own. This can be accomplished through the WHM interface > Networking Setup > Change Hostname.