When a non member visits a Post page that is members only. It has a "Join for $5 per month" button. However the button is disabled if there are no more of the lowest tier memberships remaining. Even though there are plenty for spots for example for the $7 level membership.
The post is available for all levels of memberships but the join button is canceled if there are no more spots in the lowest tier.
The button should say "Join for $7 per month" or whatever the next level that is available.