…and, as always, an hour after you post a comment you discover the answer.
This might work for you, it certainly did for me.
Look for the line ‘-webkit-appearance: none;’ in your theme CSS, delete it, and the checkbox should appear.
I’ve tried the solutions above but none are working (WordPress 3.8.1 / WooCommerce 2.1.3).
Have tried uninstalling/reinstalling WooCommerce and the plugin to no avail.
Many thanks 🙂
