This problem occurred recently – if I am not logged into WordPress, I am not able to add products to my WooCommerce cart. It redirects to the cart page as it should but shows ‘Cart Empty’. Works perfectly when I am logged in as a user in any role. I searched around and found this thread: http://wordpress.org/support/topic/plugin-woocommerce-cart-brokennot-adding-products
I’ve tried changing my session folder with a custom php.ini file but the problem is still persisting. I used Duplicator and set up an instance on my localhost – where it works without issues, so that tells me the problem isn’t with the theme or the plugins. What other issues with hosting could be causing this?
For me the error was caused by Rackspace’s “Varnish” script. it’s a server-side caching tool that they use. I don’t have more details than than. but once I alerted Rackspace, they fixed it pretty fast.