Custom Stripe Pro template not appearing

Hi,
I’m trying to customize a Stripe Pro form. I’ve copied the file stripe-checkout-form.php from the plugin/src directory to the root of my theme. My theme is a child theme of the Divi theme.

This custom form doesn’t appearing to be loading. I’ve tried putting it in the parent theme as well. Am I doing something wrong? I’ve been following the information in this page:

Thanks,
Niall