Widget problem with static front page

Hi, recently I changed front page from full with to custom template cause I wanted to add a widget. But I can not add it, and do not know why.
I do use many widget plugins, but also have two websites with Duena (child) theme and one website works very good.
The problem is with this new front page:
http://animalhealth.allimax.nl/welkom/
you can browse through the website, no other page has problems with widgets.
The website that works fine, and should be an example of what I want to achieve with problem page is:
http://humanhealth.allimax.nl/

Maybe someone can help -thank you.