Server { listen 80;

listen [::]:80;

root /var/www/domain.com/public_html;
index index.php index.html index.htm;

server_name domain.com www.domain.com;

client_max_body_size 30M;

location / {
root /var/www/domain.com/public_html;
if (!-e $request_filename) {
rewrite ^/(.*)$ /index.php?q=$1 last;
}
}

location ~ ^/(wp-admin|wp-login\.php$) {
allow xx.xx.xx.0/21;
deny all;
}

location ~ \.php$ {
try_files $uri =404;
fastcgi_split_path_info ^(.+\.php)(.*)$;
fastcgi_pass unix:/run/php/php7.0-fpm.sock;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include fastcgi_params;
fastcgi_ignore_client_abort on;
fastcgi_param SERVER_NAME $http_host;
}
}

ну так чего в error_log?