In order to add a product to the shopping cart, the product should have a price. This is Woocommerce functionality and our theme does not influence that and cannot change.
The site is adding and removing products to my cart by itself and showing the notification like the one I sent you that it says the product was removed from the list and it was never added.
I just pops the notification.
Please make the full backup of your site as well as the Theme settings export and check the issue on the Storefront theme to detect if our theme causes the problem. Storefront is a free theme developed by WooСommerce.