Paypal Checkout - 付款始终处于待处理状态

Since three days i am trying to get the Paypal Checkout to work but i always have the problem that the order is created and the money in gone from the buying account but not reaching the payee account. So here is my setup:

JavaScript 中的智能按钮整数化:

paypal.Buttons({
  
  env: enviroment,
  
  // Set up the transaction
  createOrder: function() {

    let formData = new FormData();
    formData.append('bookingId', bookingId);

    return fetch (url_createOrder, {
      method: 'POST',
      body: formData
    }).then(response => {
      console.log(response);
      return response.json()
    })
    .then(function(res) {
      console.log(res);
      return res.result.id;
    });
  },

  // Finalize the transaction
  onApprove: function(data, actions) {
    console.log(data);
    
    // This function captures the funds from the transaction.
    return actions.order.capture().then(function(details) {
      console.log(details);
      // This function shows a transaction success message to your buyer
      // window.location.href = 'danke.php';
    });
  }

}).render('#paypal-button-container');

如您所见，createOrder 开始对此脚本的 AJAX 调用:

[...]
$client = new PayPalHttpClient($environment);

$request = new OrdersCreateRequest();
$request->prefer('return=representation');
$request->body = self::buildRequestBody($price);
// 3. Call PayPal to set up a transaction
$response = $client->execute($request);
echo json_encode($response, JSON_PRETTY_PRINT);

// 4. Return a successful response to the client.
return $response;
}

private static function buildRequestBody($price) {
 return array(
   'intent' => 'CAPTURE',
   'application_context' => array(
      'brand_name' => 'Example',
        'cancel_url' => 'http://localhost/example/abbruch.php',
        'return_url' => 'http://localhost/example/danke.php'
      ),
      'purchase_units' => array(
        0 => array(
          'reference_id' => 'example_addr',
          'description' => 'example Address',
          'amount' => array(
            'currency_code' => 'EUR',
            'value' => $price
          )
        )
      )
    );
[...]

到目前为止一切正常.我得到一个 OrderId，我返回到 AJAX 调用，然后我可以插入凭据并支付给定的价格.

{create_time: "2020-08-14T19:37:59Z", update_time: "2020-08-14T19:38:20Z", id: "6FP46164U47878440", intent: "CAPTURE", status: "COMPLETED", …}
create_time: "2020-08-14T19:37:59Z"
id: "6FP46164U47878440"
intent: "CAPTURE"
links: [{…}]
payer:
address:
country_code: "DE"
__proto__: Object
email_address: "sb-ughwh2901918@personal.example.com"
name: {given_name: "John", surname: "Doe"}
payer_id: "8Z5RM2ERW6VTL"
__proto__: Object
purchase_units: [{…}]
status: "COMPLETED"
update_time: "2020-08-14T19:38:20Z"
__proto__: Object