kcsck

OK, I’ve got it! This is how I solved it:

Go to index.php in the plugin folder. At the end, you will find this:

function Ultimate_promo_form($atts)
{
	 include 'ultimate_promo_form.php';
}

Just add ob_start(); before the include and $output = ob_get_clean();return $output; after it. This is the result:

function Ultimate_promo_form($atts)
{
 ob_start();
	 include 'ultimate_promo_form.php';
$output = ob_get_clean();
    return $output;
}

And that’s it! It worked fine for me. Hope this helps. 😉