ReactJS Router Dom not navigating to dashboard after logging in - node.js

Question

Please help. I have my ReactJS NodeJS deployed on Linux NGINX and I can login on my development machine, on my phone, and on Linux OS running on my computer Oracle VM; i can accessed the application on these devices and it worked fine even when I changed IP address but immediately another device e.g somebody else computer or phone tries to login, it would always not redirect to dashboard but my three devices(laptop, phone, and Linux OS running on my computer Oracle VM) can redirect successfully to dashboard after logging in.
I have tried everything on this page below that people provided as solution but to no success :
https://stackoverflow.com/questions/43951720/react-router-and-nginx
Infact, i don't even see their login attempt in the NodeJS API running. My ReactJS build file contents are in /etc/nginx/sites-available/mydomain/ and this is my nginx.config below:
user www www; ## Default: nobody
server { # simple reverse-proxy
listen 80;
server_name mydomain;
# serve static files
#location ~ ^/(images|javascript|js|css|flash|media|static)/ {
location / {
# First attempt to serve request as file, then
# as directory, then fall back to displaying a 404.
root /etc/nginx/sites-available/mydomain;
index index.html;
try_files $uri /index.html;
}
location /api {
proxy_pass https://localhost:8084;
root /etc/nginx/sites-available/mydomain;
index index.html;
}
}
server {
listen 443 ssl;
server_name mydomain;
location / {
# First attempt to serve request as file, then
# as directory, then fall back to displaying a 404.
root /etc/nginx/sites-available/mydomain;
index index.html;
try_files $uri /index.html;
}
location /api {
proxy_pass https://localhost:8084;
root /etc/nginx/sites-available/mydomain;
index index.html;
}
ssl_certificate /etc/letsencrypt/live/mydomain/fullchain.pem; # managed by Certbot;
ssl_certificate_key /etc/letsencrypt/live/mydomain/privkey.pem; # managed by Certbot
#...
}
Please fams, what difference does it make as I have my NGINX configuration in nginx.conf and not default?
As I configured my nginx.conf do I still need to go do the same in /etc/nginx/sites-available/default and what extension is this default config file?