Passenger does not start node application - node.js

Question

Phusion passenger does not start the node app.
For error detection and to exclude my own node app errors, I have therefore used the demo app of phusionpassenger.com and the implementation description of the passenger library:
- I implement it on our own server / Infrastacture Ubuntu 16.04 LTS server (Xenial)
- we use Nginx integration mode
- For test purposes I use the open source version of Passenger
Here is an extraction of my custom generated Nginx Server block configuration file - all other integrations of the example app should be the same:
Server {
# Tell Nginx and Passenger where the public directory of your app is
root / var / www / demo / code / public;
index index.html index.htm index.nginx-debian.html;
Server name it-vergabe.de www.it-vergabe.de;
# Turn on the passenger
Passenger_Activated on;
# Tell the passenger that your app is a Node.js app
Passenger_env_var NODE_ENV development;
Passenger_startup_file app.js;
Passenger_app_type node;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-NginX-Proxy true;
proxy_pass http://localhost:3000/;
proxy_ssl_session_reuse off;
proxy_set_header Host $http_host;
proxy_cache_bypass $http_upgrade;
proxy_redirect off;
}
}
Error detection: I restart Nginx and get the typical 502 Bad Gateway error if the node application is not running. Now I start the node app in a separate terminal window:
demo # Ubuntu1604srv: /var/www/demo/code $ node app
The website now works flawlessly and error free.
I have now checked the Passenger Status with the Passenger Config application and found nothing that shows that the passenger has started and under his control the node application.
Does anyone know why that is? It makes no sense to use passenger and start the node app separately ...
Thank you - Greetings from Germany!