Update membership button not show up when user already in Free Membership

hi
I have a website: http://test.brightgreenbusinessnetwork.org.uk
user: admin
pass: 123

I have instal a plugin membership however if any user assign to FREE MEMBER Subcription then when go Subcription page there is button to upgrade to another subscription type
If user is NOT YET set to any subscription then they all show up the " Sign up " Button

You can try with this user
user: vankhoa
pass: 123