Problem CMS and Display

Hello everyone
Here is my problem.
I installed Xibo CMS on a linux ubuntu VM with Docker.
IP address: 10.39.x.x / 255.255.0.0

I have two displays that communicate without problem on the same site.

I have another display on a remote site with the following IP:
IP address: 10.38.22.x / 255.255.255.0

I have two routers between my sites for communication. (works with GLPI for example)
My viewer does not see the CMS.
I have no synchronization.
I specify that I ping the CMS address from the remote site.

Why the viewer does not see CMS?

CMS version: 1.8.2
Android version : 1.8