Woocommerce variable products order button missing

Hi,

My website is not showing a woocommerce button on pages with variable products. Ive tried the jquery bug fix, and nothing seems to help,

-all products have the same prices,
-tried bug fix

Im realy desperate now,

my website is http://www.gemaskerd-bal.nl and here is an example page that doesnt work when u add a product
http://www.gemaskerd-bal.nl/product/braziliaans-oogmasker-feest-masker-kopen/

Please help me! i dont know what to do.