Search box doesn't work

Hello,

My search box doesn’t work. At my website https://reis-vakantie.com/ the search box has following options:

* Zoekwoord (keyword) — working
* Vakanties (category) — working
* Landen (countries) — working except “alle mogelijke landen”
* Reisbureaus (stores) — Not working: the categories appears, but not the stories (I selected the stories in the search options at the general settings)