I've not heard of this problem before, but I imagine it is related to some confusion over which localized version of the XML customization files to use.
See the attached screenshot showing the folder contents of the EcoDesigner add-on. Typically, it should read the contents of the folder corresponding to your version of AC. So, if you have an "English" version in the Netherlands, then that would probably be the INT. (There is a local NED version though.)
Make sure that the INT folder contains 6 xml files, including ShadingCatalog.xml
If not, copy those files from some the USA or other folder and try again?
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB