uskhina

I had the same 525 SSL handshake issue with Cloudflare and NGINX Proxy Manager. The problem turned out to be that Cloudflare expects the backend to serve SSL on port 443, but my NPM was running SSL on a different port (like 18443). I fixed it by either mapping port 18443 to 443 in the Docker run command or compose file, or by using NGINX's internal redirect to serve SSL properly on 443. Also, make sure your Cloudflare SSL/TLS setting is set to Full (Strict) if you have a valid certificate in NPM. Once I did that and confirmed port forwarding in my router/firewall, the handshake worked fine.

I hope it helps!