Hey,
try to add this piece of code in your html:
<!--subscribe2-->
In the plugin is a function that respects the use of this deprecated code:
/**
Display form when deprecated <!--subscribe2--> is used
*/
function filter($content = '') {
if ( '' == $content || !strstr($content, '<!--subscribe2-->') ) { return $content; }
return preg_replace('|(<p>)?(\n)*<!--subscribe2-->(\n)*(</p>)?|', do_shortcode( '[subscribe2]' ), $content);
} // end filter()