title: Wordpress Ninja Forms, Access-Control-Allow-Origin and admin-ajax.php
body: <p>So, I have this WP installed on Heroku and I've installed Ninja forms to it. Despite everything working OK locally, when I push it to Heroku, the form is not submited and I receive this error through the Chrome's Console:</p>
  
  <pre><code>Failed to load https://ratts.com.br/wp-admin/admin-ajax.php: No 
  'Access-Control-Allow-Origin' header is present on the requested
  resource. Origin 'http://ratts.com.br' is therefore not allowed 
  access. The response had HTTP status code 503.
  </code></pre>
  
  <p>It's worthy to mention that this error is only delivered when I access the page via <code>http</code>, but when I access the page trough <code>https</code> the form works just fine, due to what I think to be a <code>CORS</code> problem. Anyone has any idea about how can I solve this issue? It have been three days of unsuccessful research already... rsrs</p>