How to use shortcodes within custom php files

Hello, I am currently trying to use this plugin to make users pay to view more web content. This web content is generated from a php script and so I thought inserting
<?php echo do_shortcode( '[accept_stripe_payment name="Cool Script" price="50" url="http://my_website.com/product" button_text="Buy Now"]' );?> as well as require_once('wp-load.php');
require_once('../stripe-payments/accept-stripe-payments.php'); would allow me to use this button in this page, but while the button saying “Buy Now” appears it does not do anything. Is there something I am neglecting to do to get this working or is this not possible without editing the plugin myself