I'm getting Error 521 but disabling cloudflare solves the problem

I’ve been using cloudflare for a long time, but recently I started getting the 521 error.

https://www.cloudflare.com/ips/ We have whitelisted the ip addresses written here by hosting.

When cloudflare is turned off, the problem is fixed. When cloudflare is turned on, the problem persists.

my hosting ip address: 91.227.6.17
my domain name is hasaneryilmaz.net

Hi there,

That is weird if you have whitelisted the IPs and Cloudflare not being able to communicate with your server. There is a guide on this error that I will link here;

However it is most likely an issue with Cloudflare communicating with your origin.

I tried these methods. but the result is still the same. When cloudflare is turned off, the site opens. When cloudflare is open, I get the error 521. For example, hasaneryilmaz.net and fatihmoda.com.tr are connected to the same hosting. cloudflare is closed on hasaneryilmaz.net cloudflare is on at fatihmoda.com.tr. While one site is opened, the other site is not.

I tried these methods. but the result is still the same. When cloudflare is turned off, the site opens. When cloudflare is open, I get the error 521. For example, hasaneryilmaz.net and fatihmoda.com.tr are connected to the same hosting. cloudflare is closed on hasaneryilmaz.net cloudflare is on at fatihmoda.com.tr . While one site is opened, the other site is not.