Featured product image doesn't change when I change the variables

Hi!
I have the WooCommerce plugin installed on my website – http://www.looksgoodonme.com
When you go to the product and change the variables the featured image doesn’t change, although I’ve set up an image for each variable.

What could be the problem and how do I fix it?

Looking forward to hearing from you!

Best,
Tatjana

https://wordpress.org/plugins/woocommerce/