I have good news — I solved the problem, and I really hope it helps you too!
It turned out to be something so simple from the beginning.
The issue was the port! It was blocked by the router.
After I almost gave up, I decided to monitor incoming requests to my TrueNAS instance from another PC on the network. Specifically, I sent a direct request to app.mydomain.com.
I expected to see the usual HTTP 521 error, but I wanted to confirm whether anything at all was reaching my server.
To do that, I used the following command — you can try it too:
sudo tcpdump -i any port 443 or port 80
Paste it into the TrueNAS shell and hit enter. This will put the shell into “listening” mode.
If any requests hit the server on either of those ports, you’ll see them logged in real-time.
Since I saw no output, it clearly meant that nothing was reaching the server from the router.
That brought me back to the router — I triple-checked all settings, but everything looked correct.
Then I wondered: how can I confirm whether traffic is even getting through my router at all?
The answer: online port checkers. Just Google them — for example, you can use dnschecker.org.
It showed that port 443 was blocked.
So the fix was to figure out how to unblock it. In my case, I couldn’t find any explicit option to unblock or reset ports on the router UI.
I ended up doing a factory reset on the router, then reconfigured the port forwards — and boom, it worked!
But here’s the interesting part:
You might be thinking, “Okay, but how can a server app upgrade or OS update cause a router to suddenly block ports that have worked fine for 2–3 years?”
I have a theory.
It may be due to one or both of these router features:
- DMZ
- UPnP
If these were enabled (as they were in my case), it’s possible that some network activity or update triggered the router to automatically alter port behavior.
This could explain why things stopped working without you changing anything manually.
That was a long and frustrating journey, but I learned a lot!
I hope this helps someone else solve the same issue.
Good luck!