SSL certificates will be verified for webhook payloads to HTTPS webhook addresses
API
Effective September 01, 2017
As of September 1, 2017, Shopify will begin verifying SSL certificates when delivering webhook payloads to HTTPS webhook addresses. After this date, webhooks that fail the SSL certificate verification will not successfully deliver to their hosts.
Please make sure that your server is correctly configured to support HTTPS with a valid server certificate. We suggest using a SSL checker to help you diagnose any problems with your SSL certificate installation.