Display modal popup doesn't appear

[jenkinhill]

JavaScript conflict:
TypeError: jQuery(...).fancybox is not a function

You are loading 4 different copies of jQuery. Firstly you correctly load the required VirtueMart version. Then you load these!

<script src="/components/com_imageshow/assets/js/jquery.min.js" type="text/javascript"></script>  ---- Imageshow component
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>  ---- Videobox plugin
<script src="/templates/supersignfactory233/jquery.js"></script> ---- Artisteer template

These later versions prevent the fancybox script from running so you won't get the add to cart popup.

See  http://forum.virtuemart.net/index.php?topic=119638