Variable Product not showing Add to Cart Button

Using Woocommerce, I have one Variable Product with 3 options on it.
http://www.mymumscakes.com/shop/cherry-brandy-christmas-pudding-900g-11-99/

SKU is filled in, the functions are on the template, Javascript is loading (as far as I can see). It seems that when selecting an option Woocommerce doesn’t see that an option has been selected so it keeps the Add to Cart hidden with display none.

Any way to resolve this?

http://wordpress.org/plugins/woocommerce/