502 Bad Gateway for Laravel 5.4 with nginx and php7.0-fpm in Ubuntu

I have my Laravel 5.4 app setup in Ubuntu 16.04 server with nginx and php7.0-fpm, it gives

502 Bad Gateway

Nginx virtualhost config,

server {
    listen   80; ## listen for ipv4; this line is default and implied
    #listen   [::]:80 default ipv6only=on; ## listen for ipv6

    root /var/www/html/laravel/public;
    index index.php index.html;

    # Make site accessible from http://localhost/
    server_name localhost;

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

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

Tried the following but still not working,

Changed fastcgi_pass unix:/var/run/php7.0-fpm.sock; to fastcgi_pass 127.0.0.1:9000;

Changed try_files $uri $uri/ /index.php?$query_string; to try_files $uri $uri/ /index.php$is_args$args;

Restarted service after each change,

service nginx restart
service php7.0-fpm restart

via Chebli Mohamed