Hello,
Please revisit your site and check the issue again. I have activated the core plugin, and the “Add to Cart” functionality is now working correctly.
Regarding the quantity field not appearing on the cart page, I found that it was being hidden by a custom CSS rule. I’ve commented out the following code from Appearance > Customize > Custom CSS:
.product-quantity{
display:none !important;
}
With this CSS disabled, the quantity field is now visible on the cart page.
Best Regards,