502 Bad Gateway: Cloudflare Tunnel Not Reaching Docker App on QNAP NAS

Zero Trust Cloudflare Tunnel
1

What is the name of the domain?

fotos.wortberg.org

What is the error number?

502

What is the error message?

Bad Gateway

What is the issue you’re encountering

I have a Docker application running on my QNAP NAS that I want to access externally via a Cloudflare Tunnel. However, when I try to reach the application using the public URL , I receive a 502 Bad Gateway error.

2

Does the Docker instance have the SSL certificate?
Is it listening and working on a desired port?
Are you managing and running a tunnel locally (CLI) or remotely (dashboard)?