Text filed in checkout

-- url of the page with the problem -- : www.oldehoofsterkaasboerderij.nl
-- HikaShop version -- : 2.6.1
-- Joomla version -- : 3.4.8
-- PHP version -- : 5.3.10
-- Browser(s) name and version -- : Chrome 47.0.2526.111

Good evening,

in my checkout proces, I want to give my customers the opportunity to send a message with their order. I added a 'text-area' in the checkout proces. However, the entered text is not being sent with the order.
I use Hikashop 2.6.1. essential

Thanks!

Ronald