Thank you for contacting Cloudflare. I am sorry that you are experiencing difficulties with errors.
A 525 error 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: Error 525: SSL handshake failed.
I would recommend you contact your hosting provider to make sure there aren’t the following common causes at your origin web server:
No valid SSL certificate installed
Port 443 (or another custom secure port) is not open
The cipher suites accepted by Cloudflare does not match the cipher suites supported by the origin web server
If you are only intermittently seeing 525’s, this suggests the TCP connection between Cloudflare and your origin is being reset during the SSL handshake causing the error.
In order to ensure that all requests from Cloudflare are accepted by your server over HTTPS, please make sure to:
Check if you have a certificate installed on your origin server. You can check this article for more details on how to run some tests: Gathering information. In case you don’t have any certificate, you can create and install our free Cloudflare origin CA certificate. Using Origin CA certificates allows you to encrypt traffic between Cloudflare and your origin web server.
Review the cipher suites your server is using to ensure they match what is supported by Cloudflare.
Check your server’s error logs from the timestamps you see 525s to ensure there is errors that could be causing the connection to be reset during the SSL handshake
If you are still not able to identify the cause, you can change the SSL mode to Flexible under the SSL/TLS tab in your Cloudflare Dashboard, so we do not connect to your server over port 443.
I hope this helps. However, if you have any more questions, simply reply to this email and we will be happy to help. Thank you for being part of Cloudflare!