可以'；无法从Bigcommerce API获取访问令牌，客户端ID无效

我正在尝试获取访问令牌，以便开始构建一个可与BigCommerce一起使用的应用程序。我一直在关注这里的文档：https://developer.bigcommerce.com/api/callback.我使用的是Bigcommerce的PHP客户端。

响应为HTTP/1.1 400错误请求｛"error"："无效客户端id"｝。我发誓我使用的是正确的客户端id和客户端机密！或者，至少当我在开发者门户中的草稿应用程序上单击"查看客户端ID"时，会显示它们。

我到底做错了什么？

$request = $_REQUEST;
require_once 'vendor/autoload.php';
use Bigcommerce'Api'Connection;
$tokenUrl = "https://login.bigcommerce.com/oauth2/token";
$connection = new Connection();
$connection->verifyPeer();
$connection->useUrlencoded();
$response = $connection->post($tokenUrl, array(
    "client_id" => "", //I won't type it here but it is correct
    "client_secret" => "", //also correct        
    "redirect_uri" => "https://127.0.0.1/project-custom/oauth.php", //this is the Auth Callback URL
    "grant_type" => "authorization_code",
    "code" => $request["code"], //when I echo these variables out they work
    "scope" => $request["scope"],
    "context" => $request["context"],
));  
print_r($connection->getLastError());