Funny, but it works on chrome, but not on firefox.
Strange enough there was not a single error message, it just simply didn’t work – strangest thing I have ever seen.
After some debugging, disabling the noui slider script fixed the problem. I have no idea how is that possible, since the script is namespaced to a different scope.
Anyways, to make this change persistent you will have to copy the ajax-search-pro/includes/asp_init.class.php file from the test environment to the production and set the Javascript source option on the Compatibility Options submenu to Minified.