Не выполняются несколько запросов php одновременно

Конфиг нгинкс

server {
    server_name example.ru;
    root /var/www/html/example.ru;

    index  index.php index.html index.htm;
    charset utf-8;
    gzip on;
    gzip_disable "msie6";
    gzip_comp_level 6;
    gzip_min_length  1100;
    gzip_buffers 16 8k;
    gzip_proxied any;
    gzip_types text/plain application/xml
      application/javascript
      text/css
      text/js
      text/xml
      application/x-javascript
      text/javascript
      application/json
      application/xml+rss;
    client_max_body_size            200m;
    client_body_buffer_size         128k;
    client_header_timeout           10m;
    client_body_timeout             10m;
    send_timeout                    10m;
    client_header_buffer_size       1k;
    large_client_header_buffers     4 16k;

    location /admin {
        index index.php;
    }

    location / {
        try_files $uri $uri/ @opencart;
    }


    location @opencart {
        rewrite ^/(.+)$ /index.php?_route_=$1&$args last;
    }
    
    location ~* ^.+\.(jpg|jpeg|gif|png|svg|svgz|eot|otf|woff|ttf|js|css|mp3|ogg|mpe?g|avi|zip|gz|bz2?|rar|swf)$ {
        expires max;
        etag on;
        log_not_found off;
    }
    
    location ~* (\.(tpl|ini))$ {
        deny all;
    }
    
    location ~ (?i)((\.tpl|\.ini|\.log|(?<!robots)\.txt)) {
        deny all;
    }
  
    location ~ [^/]\.php(/|$) {
      # SECURITY : Zero day Exploit Protection
      try_files $uri =404;
      # ENABLE : Enable PHP, listen fpm sock
      fastcgi_split_path_info ^(.+\.php)(/.+)$;
      fastcgi_pass unix:/var/run/php/php-fpm.sock;
      fastcgi_index index.php;
      include fastcgi_params;
      fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
      fastcgi_read_timeout 60000s;
    }


    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/example.ru/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/example.ru/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

    access_log /var/log/nginx/example.ru.access.log;
    error_log /var/log/nginx/example.ru.error.log;

}

Конфиг /etc/php/7.4/fpm/pool.d/www.conf

[www]
user = www-data
group = www-data
listen = /run/php/php7.4-fpm.sock
listen.owner = www-data
listen.group = www-data
pm = dynamic
pm.max_children = 32
pm.start_servers = 4
pm.min_spare_servers = 2
pm.max_spare_servers = 16
php_admin_value[post_max_size]=1000M
php_admin_value[upload_max_filesize]=1000M
php_admin_value[request_terminate_timeout]=0
php_admin_value[max_execution_time]=9000000s
php_admin_value[memory_limit]=512M

При этом одновременно выполняется только один запрос к PHP. То есть если запустить загрузку в товаров - сайт не открывается пока всё не загрузится.