Hi LeonGr,
Thanks for writing back. After some investigating it seems the
<base href="https://microswebsites.nl/westkaai" />
in the head of your site is causing problems with the form submitting. A base url will redirect all relative URLs contained in on the page to the url specified.
Currently, javascript form submission is disabled in the plugin settings in your site. So the forms data is submitted with html. The base url is interrupting the form information from being submitted.
To fix this, there are a few things you can try. One option is enabling Javascript Support. That can be done by checking the ‘Use Javascript Support’ option under the List Options section. Or you could remove that base tag from that specific page and the form should work.
Let us know if you have any other questions.
-mc_d