Cloudflare DNS problem

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@mervyntsao

I can not open the site

I got 521 error returned

Community Tip - Fixing Error 521: Web server is down

Error Try the suggestions in this Community Tip to help you fix Error 521: Web server is down. Background A 521 error happens when we are unable to make a TCP connection to your origin server. Specifically, Cloudflare tried to connect to your origin server on port 80 or 443, but received a connection refused error. This is often caused by security or firewall software and happens if the origin server has directly refused Cloudflare’s proxy request. [Banner in tip catalog] Quick Fix Ideas …

Before moving to Cloudflare, was your Website working over HTTPS connection?

May I ask what SSL option have you got selected under the SSL/TLS tab at Cloudflare dashboard for your domain ( Flexible, Full, Full Strict … )?

Make sure the SSL/TLS settings under the SSL/TLS tab of Cloudflare dashboard are set to Full (Strict) SSL.

Why you should choose Full Strict, and only Full Strict

Unencrypted & unverified connections Imagine you open Paypal and suddenly get that warning [image] Would you continue? Probably not. For decades leaders in IT security have advocated that people upgrade their sites from unencrypted HTTP to secure HTTPS. And for a reason, everything you send via an HTTP connection is sent in plain text and can be intercepted at any point between you and the server. Equally, you’d probably not proceed if you got such a warning, right? [image] That’s when th…

Over which port are you running your app or website?

Network ports · Cloudflare Fundamentals docs

Make sure Cloudflare IPs are allowed to connect to your origin host/server (firewall, iptables …):

Cloudflare IP addresses · Cloudflare Fundamentals docs

A list of Cloudflare’s IPv4 & IPv6 can be found here:

IP Ranges