"Error 521: Web server is down", but everything is normal

I have received a mail from cloudflare stating “Error 521: Web server is down”, but everything is normal on server.
I checked the logs and firewall rules as per suggestion. There were no error log in server, also the firewall rules allow all IPs for https. May I know what else could be the reason?
After this mail, I have added cloudflare IP ranges in firewall rules as stated here https://www.cloudflare.com/en-gb/ips/, although I suppose that should not be required as per earlier IP Should I also add [] in firewall configuration? Also, does cloudflare you inform about IP range changes or is there any place to subscribe to have email alert on cloudflare IP range changes?

@MoreHelp 2263693

This topic was automatically closed 15 days after the last reply. New replies are no longer allowed.