Apache Tomcat not visibile via the internet

[McAwesome]

I have configured on the TNAS Apache Tomcat and the Web Server. The WebServer on port 80 and Apache Tomcat on port 8080.
Similarly for both of them I opened ports on my router and routed web traffic.
The WebServer works perfectly and is visible from the outside both via noIp DDNS and via static ip.
Apache Tomcat on the other hand works locally but not remotely.
Is there anything I can check and fix, even via SSH if needed?

When I try to connect I get: ERR_CONNECTION_TIMED_OUT on chrome

[McAwesome]

If I change port from 8080 to 8081 it works? Why

[TMRyan]

Hello,
Maybe port 8080 is already occupied.

[McAwesome]

Is there any way to check on the NAS?
No other device on the network uses it.
Also if I use port 8080, locally it is possible to reach the NAS at that port, remotely not.

[TMS]

We will verify your feedback. Maybe you can see from the router whether port 8080 of the external network is occupied?

[McAwesome]

I've checked and there are no door overlaps.
In fact, if as now I leave 8081 set as port on NAS and router, from the outside on port 8080 I get an error message: ERR_CONNECTION_REFUSED; if instead I set port 8080 on the nas and on the router, the error message changes: ERR_CONNECTION_TIMED_OUT
Anyway, the support team needs to connect to my nas for another problem, can I let them know that too?

[TMS]

You can send an email to our tech team to check it remotely.