Nginx is not proxying to the node backend - express

Question

I have react application running on Nginx and backend application on Nodejs(running on another port 8080) with routes of patterns "/org-metadata/**, /proxy-api/**, /node-api/**".
I am trying to proxy the nginx to nodejs running on 8080, but it does not reach the backend. and the nginx gives the 503 Service Unavailable response and some times response 200 with You need to enable JavaScript to run this app.
Can some one pls point where am I missing anything?
Below is my nginx.conf file :
worker_processes auto;
events {
worker_connections 8000;
multi_accept on;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
server {
# listen on port 80
listen 80;
# where the root here
root /var/www;
# what file to server as index
index index.html index.htm;
location / {
# First attempt to serve request as file, then
# as directory, then fall back to redirecting to index.html
try_files $uri $uri/ /index.html;
}
# Javascript and CSS files
location ~* \.(?:css|js)$ {
try_files $uri =404;
expires 1y;
access_log off;
add_header Cache-Control "public";
}
location ~ (proxy-api|org-metadata|node-api) {
try_files $uri #nodejs;
}
location #nodejs {
proxy_pass http://nodejs:8080;
add_header X-Frame-Options "SAMEORIGIN" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header X-Content-Type-Options "nosniff" always;
add_header Referrer-Policy "no-referrer-when-downgrade" always;
add_header Content-Security-Policy "default-src * data: 'unsafe-eval' 'unsafe-inline'" always;
}
}
}