为什么PayPalHttpConnection.php响应中的PayPalConnectionException为400？

我的具体错误是：

哎呀，好像出了什么事。 PayPalHttpConnection.php第154行中的1/1 PayPalConnectionException:访问时获得Http响应代码400

据

这将为您提供错误代码和错误消息（应该会告诉您问题所在）并退出脚本

in PayPalHttpConnection.php line 154
at PayPalHttpConnection->execute('{"payer_id":"E9A9BJPWWRM8N"}') in PayPalRestCall.php line 73
at PayPalRestCall->execute(array('PayPal\Handler\RestHandler'), '/v1/payments/payment/PAY-8XG67706YY618525RLFYRHWQ/execute', 'POST', '{"payer_id":"E9A9BJPWWRM8N"}', array()) in PayPalResourceModel.php line 102
at PayPalResourceModel::executeCall('/v1/payments/payment/PAY-8XG67706YY618525RLFYRHWQ/execute', 'POST', '{"payer_id":"E9A9BJPWWRM8N"}', null, object(ApiContext), object(PayPalRestCall)) in Payment.php line 638
at Payment->execute(object(PaymentExecution), object(ApiContext)) in PayPal.php line 73
at Paypal->execute('PAY-8XG67706YY618525RLFYRHWQ', 'E9A9BJPWWRM8N') in PaymentsController.php line 16
at PaymentsController->store(object(Request))
at call_user_func_array(array(object(PaymentsController), 'store'), array(object(Request))) in Controller.php line 55
at Controller->callAction('store', array(object(Request))) in ControllerDispatcher.php line 44
at ControllerDispatcher->dispatch(object(Route), object(PaymentsController), 'store') in Route.php line 189
at Route->runController() in Route.php line 144
at Route->run(object(Request)) in Router.php line 653
at Router->Illuminate\Routing\{closure}(object(Request)) in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in SubstituteBindings.php line 41
at SubstituteBindings->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in VerifyCsrfToken.php line 65
at VerifyCsrfToken->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in ShareErrorsFromSession.php line 49
at ShareErrorsFromSession->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in StartSession.php line 64
at StartSession->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in AddQueuedCookiesToResponse.php line 37
at AddQueuedCookiesToResponse->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in EncryptCookies.php line 59
at EncryptCookies->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in Pipeline.php line 104
at Pipeline->then(object(Closure)) in Router.php line 655
at Router->runRouteWithinStack(object(Route), object(Request)) in Router.php line 629
at Router->dispatchToRoute(object(Request)) in Router.php line 607
at Router->dispatch(object(Request)) in Kernel.php line 268
at Kernel->Illuminate\Foundation\Http\{closure}(object(Request)) in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in CheckForMaintenanceMode.php line 46
at CheckForMaintenanceMode->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in Pipeline.php line 104
at Pipeline->then(object(Closure)) in Kernel.php line 150
at Kernel->sendRequestThroughRouter(object(Request)) in Kernel.php line 117
at Kernel->handle(object(Request)) in index.php line 53

try {
    //Execute payment
    $executePayment = $payment->execute($paymentExecution, $this->_apiContext);
} catch (PayPal\Exception\PayPalConnectionException $ex) {
    echo $ex->getCode(); // Prints the Error Code
    echo $ex->getData(); // Prints the detailed error message 
    die($ex);
} catch (Exception $ex) {
    die($ex);
}