Fix missing addthis toolbox buttons

your_module.module

<?php

/**
 * Implements hook_addthis_markup_alter().
 *
 * Fix addthis bug where services aren't added.
 */
function your_module_addthis_markup_alter(&$markup) {
  if (isset($markup['#display']['type']) && $markup['#display']['type'] == 'addthis_basic_toolbox') {
    $addthis_services = array_filter(variable_get('addthis_enabled_services', array()));
    $markup['#display']['settings']['share_services'] = implode(',', $addthis_services);

    // If you need custom labels.
    $labels = array(
      'google_plusone_share' => 'google+',
    );

    if (function_exists('addthis_displays_addthis_display_markup__addthis_basic_toolbox')) {
      $markup = addthis_displays_addthis_display_markup__addthis_basic_toolbox($markup);
      // Set a label for each service.
      foreach (element_children($markup) as $service) {
        if (empty($markup[$service]['#value'])) {
          if (isset($labels[$markup[$service]['#addthis_service']])) {
            $markup[$service]['#value'] = $labels[$markup[$service]['#addthis_service']];
          }
          else {
            $markup[$service]['#value'] = $markup[$service]['#addthis_service'];
          }
        }
      }
    }
  }
}