Check this thread: Rebooted VPS, now websites are not working? - #7 by lavishsphere
Check this: "ssl_stapling" ignored, no OCSP responder URL in the certificate - #10 by sahsanu
Check these ones: V-update-web-domain-ssl not working - #5 by ajmal && https://askubuntu.com/questions/256013/apache-error-could-not-reliably-determine-the-servers-fully-qualified-domain-n
These should resolve for you, afaik.