How to fix error 521 problem?

[fritex]

May I ask what known troubleshooting steps have you tried already regarding 521 error for your Website?

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 …

Troubleshooting Cloudflare 5XX errors · Cloudflare Support docs