Multiple Membership issues

Hi
i have the premium plugin and am having an issue with the multiple membership
when I have a member that has a paid membership and wants to sign up for a different membership (Volunteer) the form is saying they have already signed up although they haven’t filled out that form?

so from the front end can a member of one group(membership) sign up for another group with the full form and all?

The page I need help with: [log in to see the link]