What does “cURL error” when talking to the gateway mean?

It means Magento can’t reach the gateway’s API. cURL error 28: Operation timed out usually means a blocked outbound port or a slow firewall; cURL error 60: SSL certificate problem means an expired or missing CA bundle on the server; cURL error 6: Could not resolve host is a DNS issue. We confirm connectivity from the server, refresh the CA bundle, and re-open the outbound path so auth, capture, and refund calls succeed again.