Haven’t finished trying this, but it may be the same issue as for XML sitemaps - it needs a file rather than a folder name to fetch
I get round this using a PHP file that just reads the template churning out the XML data:
<?php
// Prevent content to be cached
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); // Content was generated on past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); //Content is always modified
// Inform user agent that content is XML and is UTF-8 encoded
header('Content-type: text/xml; charset=UTF-8');
// Read content from template and show it
@readfile ('http://shinemarketing.com/sitemap/');
?>
Just change the url in the last bit and you should be OK
It seems to accept .php as a file extension for product feeds