environment: centos7 nginx (openresty)
nginx is running normally, enter the server ip address, the website is linked and run normally, but the input domain name shows error 521, and your own server rejects the link with cloudflare. The ips of cloudflare has been added to the whitelist of iptables. Give your own server nginx.conf configuration and error.log log. Please ask the operation and maintenance partner for help. Thank you.
error.log
at present, http protocol access is normal, except for https access, and cannot be linked