Hi,
Please browse this page again:
www.flexiblewebdesign.com/Virtuemart-Extensions/Virtuemart-Flexible-Drop-Down-Shopping-Cart
This is the page you have bought the "Dropdown Shopping Cart" extension.
And now look at the screenshot:
Our dropdown shopping cart is for Virtuemart 1.1.9 ONLY, and doesn't work with Virtuemart 2.0
It is clearly declared everywhere. But your website uses Virtuemart 2.0. It is normal if it doesn't work out.
Flexible Web Design.