• Your origin web server iptables are set to trust Cloudflare IPs.
• Bad Beha vior or mod_security is up to date.
• Your htaccess file whitelist Cloudflare IPs.
• Any security plugins, such as WordPress security plugins, whitelist Cloudflare IPs. 

Similarly , For Cloudflare to send visitor requests to your origin web server, whitelist Cloudflare IP addresses at your origin web server. In addition , Contact your hosting provider or website administrator if you have questions.