NGINX/FastCGI config issues causing 404s

Question

I'm currently trying to configure a Wordpress Multisite using NGINX. The NGINX config test passes:

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

But I simply get a File Not Found. page when I load the site. From my config:

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                  '$status $body_bytes_sent "$http_referer" '
                  '"$http_user_agent" "$http_x_forwarded_for"';

    include       conf.d/*.conf;

    map $http_upgrade $connection_upgrade {
        default     "upgrade";
    }

server {
    listen        80 default_server;
    access_log    /var/log/nginx/access.log main;

    client_header_timeout 60;
    client_body_timeout   60;
    keepalive_timeout     60;
    gzip                  off;
    gzip_comp_level       4;
    gzip_types text/plain text/css application/json application/javascript application/x-javascript text/xml application/xml application/xml+rss text/javascript;

    server_name <my-domain>.com ;

    access_log   /var/log/nginx/gnbwpms.access.log;
    error_log    /var/log/nginx/gnbwpms.error.log debug;

    index index.php;

    if (!-e $request_filename) {
        rewrite /wp-admin$ $scheme://$host$uri/ permanent;  
        rewrite ^(/[^/]+)?(/wp-.*) $2 last;                     
        rewrite ^(/[^/]+)?(/.*.php) $2 last;                   
    }

    location / {
            try_files $uri $uri/ /index.php?$args ;
    }

    location ~ \.php$ {
            try_files $uri =404;
            include /etc/nginx/fastcgi_params;
            #fastcgi_pass 127.0.0.1:9000;
            fastcgi_pass unix:/var/run/php-fpm/www.sock;
    fastcgi_index index.php;
    }

    location ~* ^.+\.(ogg|ogv|svg|svgz|eot|otf|woff|mp4|ttf|rss|atom|jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|ppt|tar|mid|midi|wav|bmp|rtf)$ {
            access_log off; log_not_found off; expires max;
    }

    location = /robots.txt { access_log off; log_not_found off; }
    location ~ /\. { deny  all; access_log off; log_not_found off; }    }
}

And from my nginx error.log :

2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 01
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 07
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 00
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 01
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 00
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 16
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 02
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 00
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record length: 22
2022/01/04 14:44:43 [error] 8368#8368: *552 FastCGI sent in stderr: "Primary script 
   unknown" while reading response header from upstream, client: <client IP>, 
server: <my-domain>.com, request: "GET / HTTP/1.1", upstream: " 
   fastcgi://unix:/var/run/php-fpm/www.sock:", host: "<server IP>"
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 01
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 06
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 00
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 01
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 00
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 51
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 07
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record byte: 00
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi record length: 81
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi parser: 0
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi header: "Status: 404 Not Found"
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi parser: 0
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi header: "Content-type: text/html; charset=UTF-8"
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi parser: 1
2022/01/04 14:44:43 [debug] 8368#8368: *552 http fastcgi header done
2022/01/04 14:44:43 [debug] 8368#8368: *552 HTTP/1.1 404 Not Found

My docroot is /var/www/html and the logs seem to show requests are being sent to the right place:

2022/01/04 14:44:43 [debug] 8368#8368: *552 trying to use file: "/index.php" 
"/var/www/html/index.php"
2022/01/04 14:44:43 [debug] 8368#8368: *552 try file uri: "/index.php"
2022/01/04 14:44:43 [debug] 8368#8368: *552 generic phase: 14

Not really sure where to go from here, so any help would be greatly appreciated.

Answer 1

Glad you managed to sort this. As mentioned in my comment, adding the following line to your server block resolved the issue:

SCRIPT_FILENAME $document_root$fastcgi_script_name