Ah… now I get the message:
SyntaxError: Unexpected token < in JSON at position 0
I enabled debugging but the only log I get for the payment that is not working is this one:
07-12-2018 @ 12:58:45 – getUserMollieCustomerId: Mollie Customer ID (XXXXXXXX) found and valid for user 1 on this API key. (live).
07-12-2018 @ 12:58:45 – mollie_wc_gateway_creditcard: Order 5944 webhookUrl: https://www.zwangerschaps.nl/wc-api/mollie_wc_gateway_creditcard/?order_id=5944&key=wc_order_5b473464d0aea
