Paypal IPN未在沙箱中调用

Question

我可以创建并执行付款。我可以使用IPN模拟器来模拟Express Checkout，并且可以正常工作。我无法连接2。我认为这是我在执行付款代码中正在执行或未执行的操作。这是代码：

<?php
    require "vendor/autoload.php";
    use PayPal\Api\Amount;
    use PayPal\Api\Details;
    use PayPal\Api\Payment;
    use PayPal\Api\PaymentExecution;
    use PayPal\Api\Transaction;

    $apiContext = new \PayPal\Rest\ApiContext(
        new \PayPal\Auth\OAuthTokenCredential(
            '(*ClientID*)',
            '(*ClientSecret*)'
        )
    );

    $paymentId = $_GET['paymentId'];
    $payment = Payment::get($paymentId, $apiContext);

    $execution = new PaymentExecution();
    $execution->setPayerId($_GET['PayerID']);

    $transaction = new Transaction();
    $amount = new Amount();
    $details = new Details();

    $details->setShipping(0)
        ->setTax(0)
        ->setSubtotal(10);

    $amount->setCurrency('USD');
    $amount->setTotal(10);
    $amount->setDetails($details);
    $transaction->setAmount($amount);

    $execution->addTransaction($transaction);

    try {
        $result = $payment->execute($execution, $apiContext);
        return $result;
    } catch (\PayPal\Exception\PayPalConnectionException $ex) {
        // This will print the detailed information on the exception.
        //REALLY HELPFUL FOR DEBUGGING
        echo $ex->getData();
    }
?>

我已经遍历了很多次。所有默认设置等都是正确的。我没办法尝试了。