'Cannot GET' on Nodejs when using proxy pass in Nginx - node.js

Question

I'm running Nginx & NodeJS on Jelastic Paas, and need a Nginx reverse proxy to direct to a React app on a Nodejs.
I'm getting a "Cannot get/" error message, and not sure if it's on the Nginx or nodejs side, I did the same configuration on an other environment without any problem.
Question:
Is there something I'm forgetting?
Is the following configuration correct?
http {
server_tokens off ;
include /etc/nginx/mime.types;
default_type application/octet-stream;
set_real_ip_from <PRIVATE IP>;
set_real_ip_from <PRIVATE IP>;
set_real_ip_from <PRIVATE IP>;
real_ip_header X-Forwarded-For;
real_ip_recursive on;
log_format main '$remote_addr:$http_x_remote_port - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for" '
'"$host" sn="$server_name" '
'rt=$request_time '
'ua="$upstream_addr" us="$upstream_status" '
'ut="$upstream_response_time" ul="$upstream_response_length" '
'cs=$upstream_cache_status' ;
client_header_timeout 10m;
client_body_timeout 10m;
send_timeout 10m;
client_max_body_size 100m;
connection_pool_size 256;
client_header_buffer_size 1k;
large_client_header_buffers 4 2k;
request_pool_size 4k;
gzip_min_length 1100;
gzip_buffers 4 8k;
gzip_types text/plain;
output_buffers 1 32k;
postpone_output 1460;
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 75 20;
ignore_invalid_headers on;
map $upstream_addr $group {
default "";
.<PRIVATE IP>:80$ common;
}
upstream default_upstream{
server <PRIVATE IP>;
sticky path=/; keepalive 100;
}
upstream common { server <PRIVATE IP> ; sticky path=/; keepalive 100; }
server {
listen *:80;
listen [::]:80;
server_name _;
access_log /var/log/nginx/localhost.access_log main;
error_log /var/log/nginx/localhost.error_log info;
proxy_temp_path /var/nginx/tmp/;
proxy_connect_timeout 5s;
error_page 500 502 503 504 /50x.html;
proxy_next_upstream error timeout http_500;
proxy_http_version 1.1;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Host $http_host;
proxy_set_header X-Forwarded-For $http_x_forwarded_for;
proxy_set_header X-Remote-Port $http_x_remote_port;
proxy_set_header X-URI $uri;
proxy_set_header X-ARGS $args;
proxy_set_header Refer $http_refer;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
if ($http_x_remote_port = '' ) {
set $http_x_remote_port $remote_port;
}
location = /50x.html {
root html;
}
location / {
if ($cookie_SRVGROUP ~ group|common) {
proxy_pass http://$cookie_SRVGROUP;
error_page 500 502 503 504 = #rescue;
}
if ($cookie_SRVGROUP !~ group|common) {
add_header Set-Cookie "SRVGROUP=$group; path=/";
}
proxy_pass http://default_upstream;
add_header Set-Cookie "SRVGROUP=$group; path=/";
}
location #rescue {
proxy_pass http://default_upstream;
add_header Set-Cookie "SRVGROUP=$group; path=/";
}
}
include /etc/nginx/conf.d/*.conf;
}

Answer 1

Here is the message I'm getting