PayPal REST API 为信用卡令牌返回 500 服务器错误

This is the code I am using (I apologize if there is too much information here, I didn't know what information was pertinent to my problem)

<?php
include("bootstrap.php"); //Sample bootstrap file configured with my clientId and Secret, creates $apiContext
use PayPalApiCreditCard;
use PayPalApiPayer;
use PayPalApiFundingInstrument;
use PayPalApiDetails;
use PayPalApiAmount;
use PayPalApiTransaction;
use PayPalApiPayment;
use PayPalApiAddress;
use PayPalApiCreditCardToken;

$useVault = true;

$addr = new Address();
$addr->setLine1('52 N Main ST');
$addr->setCity('Johnstown');
$addr->setCountry_code('US');
$addr->setPostal_code('43210');
$addr->setState('OH');


$card = new CreditCard();
//Also used PayPal Sandbox account number here
$card->setNumber('4111111111111111');
$card->setExpire_month('03');
$card->setExpire_year('2019');
$card->setCvv2('123');
$card->setFirst_name('Joe');
$card->setLast_name('Shopper');
$card->setType('visa');
$card->setBilling_address($addr);
$fi = new FundingInstrument();

//Setting $useVault to false here
// will attempt to make the payment without storing the CC in the vault
// Which works. having it use the vault will return a 500 error
if($useVault){
    //use Store the CC in the vault
    $response = $card->create($apiContext);
    $ccToken = new CreditCartToken();
    $ccToken->setCredit_card_id($response->id);
    $fi->setCredit_card_token($creditCardToken);
}else{
    $fi->setCredit_card($card);
}


$payer = new Payer();
$payer->setPayment_method('credit_card');
$payer->setFunding_instruments(array($fi));
$amountDetails = new Details();
$amountDetails->setSubtotal('7.41');
$amountDetails->setTax('0.03');
$amountDetails->setShipping('0.03');


$amount = new Amount();
$amount->setCurrency('USD');
$amount->setTotal('7.47');
$amount->setDetails($amountDetails);
$transaction = new Transaction();
$transaction->setAmount($amount);
$transaction->setDescription('This is the payment transaction description.');

$payment = new Payment();
$payment->setIntent('sale');
$payment->setPayer($payer);
$payment->setTransactions(array($transaction));
try {
    var_dump($payment->create($apiContext));
} catch (PayPalExceptionPPConnectionException $ex) {
    echo "Exception: " . $ex->getMessage() . PHP_EOL;
    var_dump($ex->getData());
    exit(1);
}

如果我将 $useVault 更改为 false，那么将付款并且交易将显示在开发人员沙箱中.我在 dev-tools.paypal.com 上使用了本指南 它似乎和我有同样的问题(我到达第 3 步，共 4 步，它打印出发生内部服务错误