The plugin causes a "notice" in WordPress:
Notice: is_feed was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. Please see Debugging in WordPress for more information. (This message was added in version 3.1.) in /home/nettsite/domains/wp-sandbox.nettsite.co.za/wordpress/wp-includes/functions.php on line 2962
I don't known if that is the reason, but the URL to the CSS files provided by WP_Minify is invalid, and no CSS is loaded at all.
HTML is not minified at all, looks pretty normal to me when "viewing source" in Google Chrome.
Didn't find the minified JS, maybe I missed it, maybe the plugin missed it.