Hi,
You're the second person reporting that issue, and the first person was also from the Netherlands.
He told us that using iDEAL, it worked for him.
Otherwise, could you try again and look at the response from the AJAX request in the "networks" tab of the console of your browser when you have the error ?
It should explain why the payment request was rejected. Normally, we have some code in the payment plugin to catch that reason and display it but maybe there is a problem there. So it would help if you could provide the information as we're not able to reproduce the issue.
As an alternative, I would recommend you go through the checkout and use instead the "credit card" payment method or the "bank transfer" payment method. The credit card payment method will go through another payment gateway than PayPal and thus you should not have a problem. As for the bank transfer, if you can provide the receipt from your bank we can confirm your order without waiting to receive the funds in our bank account.