you only have the Populate list from array behavior.
you also need to have the set selected in list behavior applied.
you should have 3 behaviors:
1) Set selected in list to select the parent list
2) Populate list from array to populate the child list
3) Set Selected in list to select the item in the child list.
if you need me to look at this further, i need the login details to access the page in your link, and also the FTP information to access the page directly.