Upon clicking the 'Add To Cart' button on any product I am redirected to the correct cart page but the shortcode doesn't seem to be firing at all. It's not putting up the 'empty cart' message when the cart is empty either. Seems like the cart shorcode is simply not executing at all and nothing is being rendered. Nothing in the debug file either, I have no idea what's going on. Site is below if you'd like to try it out.
http://www.sinnerstosaints.com/store
https://wordpress.org/plugins/wordpress-simple-paypal-shopping-cart/