Description: This error happens when your site generates a 500-599 server error when we try to scan it. It might be a temporary error, but it can also be related to a malicious injection gone wrong and breaking the site. The most common codes are listed below; please find the one you see in the SiteCheck results.
You can also contact your web hosting company for more details (since it could be related to something they are doing).
500 Internal Server Error
This status code usually means a PHP error or a server configuration error. Please check your web server logs for the error message. This error can also be caused by malware.
502 Bad Gateway
This status code means the upstream server send an invalid response to a proxy or a WAF. If your website is behind a proxy or a WAF, please check that the origin server (your server, not WAF) is functioning correctly. Try to scan the website again by clicking Force a Re-scan link at the bottom of the SiteCheck results page.
503 Service Unavailable
Your web server is overloaded, down for maintenance, or down because of malware. Please check that you can access your web server in a web browser. Try to scan the website again by clicking Force a Re-scan link at the bottom of the SiteCheck results page.
504 Gateway Timeout
This status code means the upstream server was unable to respond in time. If your website is behind a proxy or a WAF, please check that the origin server (your server, not WAF) is up and running. Try to scan the website again by clicking Force a Re-scan link at the bottom of the SiteCheck results page.
508 Loop Detected
This is usually a temporary error. Please check if your website is up and running. Try to scan the website again by clicking Force a Re-scan link at the bottom of the SiteCheck results page.
520 Web Server Returns an Unknown Error (CloudFlare)
521 Web Server is Down (CloudFlare)
522 Connection Timed Out (CloudFlare)
523 Origin is Unreachable (CloudFlare)
524 A Timeout Occurred (CloudFlare)
525 SSL Handshake Failed (CloudFlare)
526 Invalid SSL Certificate (CloudFlare)
See the CloudFlare website.
If you are using Sucuri WAF, see also Sucuri WAF documentation for status codes.