“Your cart is currently empty” on checkout page

its adding successfully. i tested it.

So why would it not be working at my url?

I tested it on your website only . its adding to the cart. https://drive.google.com/file/d/1GKlZdYXSEMy_NS1OmOkVkPfla-Cysgek/view

What you clicked on in the screencast was not the link to the single page checkout page. You clicked on the page for the ordinary woocommerce product page, showing the product that I am trying to add to the single page checkout page unsuccessfully. The single page checkout page, that isn’t working, is the link at the bottom of my post, https://prost.asia/donate/.