A short while ago I had the hosting company of one of my clients add a SSL certificate to their website (www.mirjam-ouwerkerk.nl). Since then the webhooks fail to complete. The return status code is zero and when I hover over the status code the little hover text says "unable to verify the first certificate".
The reason I am reaching out to you first is that no browser has problems with the certificate (even on old Android 7 hardware) and also the payment provider we use has no problems calling webhooks to update payment information.
Any help is greatly appreciated.