AJAX WP

arquivo javascript
//code ajax of loading feed of facebook
    var skipFb = 0;

    $('.button-feed-fb').click(function(e) {

      var idFeedFb = e.target.id;
      
      if (idFeedFb === 'prev-feed-fb') {
        if (skipFb > 0) {
          skipFb--;
        }
      }else {
        skipFb++;
      }

      $.ajax({
        url: ajaxurl,
        type: 'POST',
        data: {
          'action' : 'get_feed_fb',
          'skip' : skipFb
        },
        success: function( response ){
          $('.facebook-content').html(response);
        }
      });
    });
    
    
    funcao do arquivo function.php
    
  // Get the feed if facebook with paginate
  function get_feed_fb() {
    $skip = $_POST['skip'];
    $urlRequest = "https://graph.facebook.com/tagon8/feed?access_token=989691144406052|xGG3uZqUmL9b1ycUlqbXj6MPlEw&limit=1&offset=$skip";

    $JSONcontent = file_get_contents($urlRequest);
    $graphObject = json_decode($JSONcontent);
    ?>
    <p class="bolder content-title">
      <?php
        setlocale(LC_ALL, "pt_BR", "pt_BR.iso-8859-1", "pt_BR.utf-8", "portuguese");
        date_default_timezone_set('America/Sao_Paulo');
        echo strftime("%A, %d de %B de %Y", strtotime( reset($graphObject->data)->created_time ));
      ?>
    </p>
    <p class="content-text">
      <?php echo reset($graphObject->data)->message; ?>
    </p>
    <?php
    wp_die();
  }

  add_action('wp_ajax_nopriv_get_feed_fb', 'get_feed_fb');

Arquivo JavaScript

• Chama um método error para ver qual tipo de erro ele retorna no console.

...
error: function(errorThrown) {
    console.error(errorThrown);
} 

functions.php

• Passa um escape no POST.

$skip = mysql_real_escape_string($_POST['skip']);

• No final:

add_action('wp_ajax_nopriv_get_feed_fb', 'get_feed_fb');
add_action('wp_ajax_get_feed_fb', 'get_feed_fb');

Tenta passar: async: false no objeto XHR do seu script.