Intermittent SSL errors have returned

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Now I receive a different error, 521:

For troubleshooting 521 error:

Troubleshooting Cloudflare 5XX errors | Cloudflare Support docs

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 …

May I ask over which HTTPS port does your app work? Is it default 443 or some other on the origin server?

Are you using some kind of a proxy there?

Are Cloudflare IPs allowlisted?

IP Ranges

May I ask if you’ve already went through the troubleshooting steps from below article ?:

Community Tip - Fixing Error 525: SSL handshake failed

Error Try the suggestions in this Community Tip to help you fix Error 525: SSL handshake failed. Background Error 525 indicates that the SSL handshake between Cloudflare and the origin web server failed. This only occurs when the domain is using Cloudflare Full or Full (Strict) SSL mode. This is typically caused by a configuration issue in the origin web server, when this happens, you’ll see “Error 525: SSL handshake failed”. [Screen Shot 2022-01-27 at 12.55.03 PM] Quick Fix Ideas If you…