Nginx for reversing proxy on guacamole but RDP not working on External LAN with proxy

I use Nginx on Ubuntu 16.04 for using Guacamole as RDP clientless. This is working perfectly on my computer which is in an external LAN. But not working in another external LAN which have proxy (work area). When I go to the app from my browser : http://myserverguaca/guacamole/ I can see log-in page and I can log on. But when I try to start the RDP there is a loading, then a message that says: The server take to many to time to be respond. Do you think I have to forward another port ? I have forwarded the port 8080 to 80, RDP use : 3389, but this is in localhost, don't know why I should forward this too and how I can do it. There is the configuration of my RDP access (user-mapping.xml) rdp localhost 3389 fr-fr-azerty true and my config on nginx (sites-enabled/guacamole) server { listen 80; server_name vpsmyserver.net.com; location /guacamole/ { proxy_pass http://localhost:8080/guacamole/; proxy_buffering off; proxy_http_version 1.1; proxy_set_header X_Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection $http_connection; access_log off; } }