[Plugin: Bol.com Partner Program] Cannot select products

I’m using the Bol.com plugin for an affiliate program.
I’m using it a two sites and on one site it works fine.

But at https://www.bouwzelfjezwembad.nl I can’t use it. When I make a productlink it selects immediately step 2. So you can’t select any product. I had earlier the same problem, it disappeared for a while and now it’s the same.

What can be the problem?