Question

A web application server suddenly fails to connect to an external API, logging TLS errors like 'certificate is not yet valid'. The certificate has a valid date range confirmed by the API vendor, and DNS resolves correctly. You run 'timedatectl' and see the local time is set several days in the past, with NTP synchronization inactive. What is the MOST likely root cause of the connection failure?

Accepted Answer

The server's system clock is skewed into the past, so the certificate's validity start date is in the future relative to the server, causing validation to fail

Answer

The API vendor's certificate chain is missing an intermediate CA that must be installed in the local trust store

Answer

The firewall is blocking outbound port 443, preventing the TLS handshake from completing

Answer

The server's /etc/resolv.conf points to a stale DNS cache returning an outdated certificate fingerprint