To allow the EdgePort CDN to function properly you need to add the following to the NGinx app server config:

/conf.d/site-default.conf

add_header Access-Control-Allow-Origin *;
add_header Access-Control-Allow-Methods 'GET, POST, OPTIONS';

This is generally added to the correct section where you see:

add_header X-Frame-Options "SAMEORIGIN";

Also within the location tag you need to add (important for Magento - inside the static and pub locations):

 if ($request_method = 'OPTIONS') {
   add_header 'Access-Control-Allow-Origin' '*';
   add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS';
   add_header 'Access-Control-Allow-Headers' 'DNT,Authorization,X-CustomHeader,Keep-Alive,User-Agent,Origin,Referer,X-HTTP-Method-Override,X-Accept-Charset,X-Accept,Accept,Access-Control-Request-Method,Access-Control-Request-Headers,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type';
   add_header 'Access-Control-Max-Age' 1728000;
   add_header 'Content-Type' 'text/plain charset=UTF-8';
   add_header 'Content-Length' 0;
  return 200;
 }

 location ~* \.(ico|jpg|jpeg|png|gif|svg|js|css|swf|eot|ttf|otf|woff|woff2)$ {
   add_header Cache-Control "public";
   add_header X-Frame-Options "SAMEORIGIN";
   add_header Access-Control-Allow-Origin *;
   add_header Access-Control-Allow-Methods 'GET, POST, OPTIONS';
   expires +1y; 
 }