React Router BrowserRouter leads to “404 Not Found – nginx ” error when going to subpage directly without through a home-page click

The problem is that nginx doesn’t know what to do with /signin. You need to change your nginx config (usually in /etc/nginx/conf.d/) to serve your index.html regardless of the route. Here is a sample nginx config that might help:

server {
  listen 80 default_server;
  server_name /var/www/example.com;

  root /var/www/example.com;
  index index.html index.htm;      

  location ~* \.(?:manifest|appcache|html?|xml|json)$ {
    expires -1;
    # access_log logs/static.log; # I don't usually include a static log
  }

  location ~* \.(?:css|js)$ {
    try_files $uri =404;
    expires 1y;
    access_log off;
    add_header Cache-Control "public";
  }

  # Any route containing a file extension (e.g. /devicesfile.js)
  location ~ ^.+\..+$ {
    try_files $uri =404;
  }

  # Any route that doesn't have a file extension (e.g. /devices)
  location / {
    try_files $uri $uri/ /index.html;
  }
}