URL issue on Ubuntu Nginx Multi Store setup on EC2

[DPMWines]

Please help, can't seem to figure this one out.

Magento 2.1.3 is setup with 3 stores in the backend but on the Front End, the behavior is as follows :

- site1.com (set as default) is working fine when landing on the home page except that when looking up product catalog the url switches back to the EC2 public DNS

-  When looking up site2.com, home page is working fine as well but the same behavior as site1.com happens and on top is goes back to site1.com product catalog.

etc/nginx/sites-available/magento looks like this :

upstream fastcgi_backend {
  server   unix:/run/php/php7.0-fpm.sock;
}

map $http_host $MAGE_RUN_CODE {
   default '';
   test.site1.com code1;
   test.site2.com code2;
   test.site3.com code3;
}

server {
    listen 80;
    server_name test.site1.com test.site2.com test.site3.com;
    set $MAGE_ROOT /var/www/html/Magento;
    set $MAGE_MODE developer; # or production

    access_log /var/log/nginx/Magento-access.log;
    error_log /var/log/nginx/Magento-error.log;

    include /var/www/html/Magento/nginx.conf.sample;
}

nginx.conf.sample section as follows:

# PHP entry point for main application
location ~ (index|get|static|report|404|503)\.php$ {
    try_files $uri =404;
    fastcgi_pass   fastcgi_backend;
    fastcgi_buffers 1024 4k;

    fastcgi_read_timeout 600s;
    fastcgi_connect_timeout 600s;

    fastcgi_param MAGE_RUN_TYPE website;
    fastcgi_param MAGE_RUN_CODE $MAGE_RUN_CODE;

    fastcgi_index  index.php;
    fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
    include        fastcgi_params;
}