this is the cause of the error. an html page is a static page. DataAssist cannot be applied to a static html page.
you must create a dynamic page, save it to your site and have this page open before starting the wizard. the dynamic page that you have open tells DataAssist what language to create the pages in.
create an index.php page, save it to your site and have that page open to tell DataAssist that you what it to create PHP pages.