On the CComment dashboard, there is a statement: "You must enter your Download ID before you can update CComment Professional using the update functionality of Joomla. For more information, please read our instructions.". But the link is https://compojoom.com/support/documentation/ccomment/ch02 and this gives a 404 error.
BTW I don’t think a 404 on the Compojoom site should count as one of the (parsimonious) 5 tickets per year!