My NEOS website can't find any images or CSS when I access it via IPv4, even though everything works fine via IPv6

When accessed via non-standard port numbers, NEOS automatically attempts to adjust the generated links so that they also use those port numbers. Since we route IPv4 traffic through the upstream proxy to different port numbers on the web server, this causes problems. To work around this, you can instruct the web server to ignore the actual port number and simply use 443 for SSL.

For newer installations, we’ve resolved this by adding the following section at the end of /usr/local/etc/nginx/include/neos.conf:

location ~ \.php$ {
  include /usr/local/etc/nginx/fastcgi_params;
  try_files $uri =404;
  fastcgi_pass unix:/var/run/php-fpm/php-fpm.socket;
  fastcgi_index index.php;
  fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
  fastcgi_param PATH_INFO $fastcgi_path_info;
  fastcgi_param FLOW_REWRITEURLS 1;
  fastcgi_param FLOW_CONTEXT Production/Local;
  fastcgi_param X-Forwarded-For $proxy_add_x_forwarded_for;
  fastcgi_param X-Forwarded-Port $proxy_port;
  fastcgi_param SERVER_NAME $http_host;
  fastcgi_param SERVER_PORT 443;
  fastcgi_split_path_info ^(.+\.php)(.*)$;
  fastcgi_read_timeout 300;
  fastcgi_buffer_size 128k;
  fastcgi_buffers 256 16k;
  fastcgi_busy_buffers_size 256k;
  fastcgi_temp_file_write_size 256k;
}

In older installations, the line "fastcgi_param SERVER_PORT 443;" is missing from the file. This line must be added, and nginx must be restarted once using "service nginx restart".