Website loads pefectly local but only title on network

I've built a website using Clojure (Luminus Framework) and I've deployed to Tomcat 9.0 to a Linux server.

I've done this at the company network and I am able to surf the website using http://localIP:8080 and http://externalIP:8080

But I'm installing in a client network, same Linux distribution (Debian), same Tomcat 9 and Java version (1.8).

The problem is that I can surf the web site through http://localIP:8080 but when I go to http://externalIP:8080 it loads only the title/header partially (see the imagem below).

External access

Internal access

I couldn't figure it out through tomcat logs, the output are the same as in my network.

Im guessing it is some kind of port or ip conflict, but how can I kind of debug this? I do not have control to this network, because it is from a client.

I appreciate in advance.