add to cart button lost

-- url of the page with the problem -- : www.borduurshopanita.nl
-- HikaShop version -- : 2.6.3
-- Joomla version -- : 3.5.1
-- PHP version -- : 5.6.21
-- Browser(s) name and version -- : chrome

hi,
I am having problems with add to cart button.
After playing around with the settings I lost it.
I tried the change the settings on the add to cart in the display menu, also the free product button setting and the button style in the display menu without any positive result.
I am really lost in finding the solution of this problem.
Please advise.