Learn how to deal with the various HTTP error response codes that you may encounter on your website.
503 – Service Unavailable
520 – Origin Server Unavailable
A 520 error indicates that the QUIC.cloud PoP was unable to connect to the origin server. Most likely, the issue is a firewall at the origin server blocking connections. This is problematic because QUIC.cloud acts as a proxy service for your domain, and requires access for uncached requests.
Hosts that are running LiteSpeed Web Server v5.4.12 or newer, and those that use the Imunify360 and BitNinja security systems don’t have to worry about this, because new or changed IPs are automatically updated under these systems. If you use a different security system that can pull from an IP list, please let us know and we’ll contact them!
If your server is not using any server-level firewall, or the IP’s have been added already, see if you have an application-level firewall in use, such as Wordfence or Securi. It should include a similar allowlist function.
521 – Origin Server Timeout
A 521 error indicates that the connection between the QUIC.cloud PoP and your origin server timed out. This just means that there was no activity for a lengthy period of time, and the connection is assumed to be dead. Check that your origin server is up and running.