Add to cart button missing woocommerce

Hi

I have noticed i am missing my “add to cart” button in woocommerce on products with a variation.
I have spent the last two days trying to figure out why this button is missing. I have tried every solution i could find but nothing seems to work.

I have filled every field under each variation and do not run any form of cache or minify plugins.

i am currently running:
Wordpress 3.8.1
WooCommerce 2.1.6
Media Library Category 1.4.8

one of the products is on this link: http://www.croft.dk/?product=tarp-duffle