After updating a theme (I was using The Retailer) and WordPress (to 4.1) I was missing the add-to-cart button in WordPress / WooCommerce webstore for variable products (products with variations).
First, what I tried to get the add-to-cart button back to working:
– change the template (to see if it’s the template’s fault)
– turn all plugins off and on again to see if any plugins are conflicting
– see in the CSS – the button area has a display: none set to it, when changing CSS to visible, add to cart button appears but after adding to cart got a “Please choose product options”
– create a new simple product – the add to cart button was present!
– see the debugger in Firefox returning a error 404 to jquery.cookie.min.js
Here is how I solved the missing add-to-cart button problem
1. Download and install a plugin called WooCommerce jQuery Cookie Fix
from this WooThemes Docs article https://docs.woocommerce.com/document/variable-product/#section-10
Or from here directly: woocommerce-jquery-cookie-fix.zip
It seems that you are a good person and updated all your software, but the server-side configuration that you probably cannot touch needs to be updated too. This plugin will solve your add-to-cart button easily.
Spent 2 hours figuring this out. Hope this helps!