I was setting up WordPress (this one to be specific) on TrueNAS Scale with Nginx and Cloudflare handling the proxy solution. I installed it as an app, mapped the appropriate port, and everything looked fine—until I tried routing it through Nginx Proxy Manager (NPM) with my custom domain.

502 Bad Gateway.

Not ideal.

The Setup

• TrueNAS Scale hosting WordPress via an app install (192.168.xxx.xxx:xxxxx).
• Nginx Proxy Manager handling SSL and domain routing (danielgt.com).
• Let’s Encrypt certs for HTTPS via Nginx SSL management.

I tried pointing NPM to the internal IP and port like I would normally do with a service. HTTPS just died with a 502, and HTTP sat there loading indefinitely.

The Fix

The issue seemed to be due to SSL settings. I wish this was some knowledge that just jumped out at me, but it took a bunch of fiddling with a number of app reinstalls. Things started working when I made these updates to my SSL Settings inside of NPM.

Enable Force SSL

Enable HTTP/2 Support

Finally inside of WordPress, I made the update that had been making my installs inaccessible previously. Inside Settings -> General I updated the urls and did a force refresh to the front end due to some caching issues.

Final Thoughts

Nginx normally makes things SUPER easy, this was kind of a surprise as once I had my Cloudflare + Nginx setup finished previously, making apps accessible was always super easy. This seems to be an issue with how WordPress and my configuration interacted which I think is abnormal.