facebook sdk api 5视频缩略图不是设置

Question

大家好日子。我有问题通过facebook sdk api设置视频缩略图5.视频上传后，但没有我的缩略图。你能帮助我吗... 有什么办法吗？上传时我没有任何错误。有我的代码......

    $timer = time();
    $fb = new Facebook\Facebook([
        'app_id'  => $app_id,
        'app_secret' => $app_secret,
        'default_graph_version' => 'v2.8',
    ]);
    $linkData = [
      'thumb'  => $fb->fileToUpload('http://SITE_NAME/upload/thumb.jpg'),
      'source' => $fb->videoToUpload('http://SITE_NAME/upload/test.mp4'),
      'title'  => 'VIDEO TITLE',
      'description' => 'VIDEO DESCRIPTION',

    ];
      $response = $fb->post("/me/videos", $linkData, $token);

    $graphNode = $response->getGraphNode();
    $timer_ = time();
    echo 'Posted time in '.($timer_ - $timer).' seconds with id: ' . $graphNode['id'];
    ?>