Subscriber, cannot join free membership.

If there is a subscriber that has no member level assigned to it and they try to log into the members area they are redirected to a page that says "
Protected Content, The content you are trying to access is only available to members. Sorry." with a subscribe button. This makes sense as they haven't subscribed to a membership level however, if they click the subscribe button at this point nothing happens... Shouldn't there be an opportunity at this point for this person to subscribe? If I click subscribe, the same page just loads again - nothing happens. Ideally, I would like them to be able to go to the memberships page and select the membership to subscribe to...