Mmm. I had a closer look but we actually had to remove the popup with the cart previously as it wasn't working properly in some cases with other things and was never used once yet.
So that's why the popup is not showing.
It's still possible but it requires PHP to be inserted in the page. Since the cart is no displayed on the page, you could add the code below at the beginning of the cart file of the view product via the menu Display->Views:
if(JRequest::getInt('popup')){
$class = hikashop::get('helper.cart');
$class->getJS(urlencode(hikashop::currentURL()));
$doc =& JFactory::getDocument();
$js = '
do_nothing( function() {
SqueezeBox.fromElement(\'hikashop_notice_box_trigger_link\',{parse: \'rel\'});
});
';
$doc->addScriptDeclaration("<!--\n".$js."\n//-->");
}
That will add the popup code in the cart module so that it can be displayed when necessary.