I've tried to launch a Node.js app either with systemd or cron both with unprivileged and privileged accounts but it seems that the only way to get it work is with node app.js or whatevermonitoringpackage app.js. I'm using nginx as a reverse proxy, so my first guess was to check if nginx's logs had some errors but nothing. Then I tried to launch it directly by http://IP:PORT but nothing. My firewall's rules are ok, triple-checked. Browsers say "Waiting...". systemd works normally and cron is normally executed at startup. There are no errors.

Thanks in advance.