Hello Esmi,
Sorry voor my short question.
More information: WordPress 3.9.1
Theme: Child Theme (variant Twenty Ten)
Bol.com partner plugin for WordPress version: 1.3.0 (the plugin for affiliate partners to place bol.com products).
If I want to insert a product link I see the message:
Error: No categories could be picked up at the bol.com API
A screenshot https://inbakeren.nl/images/screenshot-nieuw-product.jpg
Bol.com has checked the API code, this is correct. They also tested the plugin and it works properly.
Is this enough information?