It seems that the device doesn’t have the agent installed, only the configuration profile, because that is the section from where you can push the security package. In Device List, under ‘Active Components’ column, the ‘AG’ component has a green or a grey background?
Ok had another look at the enrolment page and there were 2 links on it for the mac, I have installed them both and now the button is available. It was a few months back when I set it up so it probably didn’t have a client before