URGENT please: Nginx does not do name resolution from a client workstation

I have a huge problem. I am a beginner and I do not understand. yet I am documenting myself. I want from a client pc to access the default website installed via the nginx service. This is thanks to my configured domain name. Indeed, I want to set up a local network. all machines will have to access the site from the local domain name. Unfortunately, this is only possible with the local IP address of the server. the dns is configured, also the firewall. I specify here that everything works at the server level. But not on the client workstation. What to do?

the site is located at /var/www/matrix.cer/html/index.html
the configuration made on nginx is at / etc / nginx / sites-available / default

the modification added to the file in question is as follows:

server {
listen 80;
listen [::]:80;

root /var/www/matrix.cer/html;
index index.html;

server_name matrix.cer.org www.matrix.cer.org;

location / {
try_files $uri $uri/ =404;
}
}

on the client pc browser is displayed:

This site cannot be accessed Cannot find the server IP address
_PROBE_FINISHED_NXDOMAIN