Paypal SetExpressCheckout(快速结账) 10731异常,请有经验的人帮忙

var expResponse = client.SetExpressCheckout(ref csh, new SetExpressCheckoutReq()
            {
                SetExpressCheckoutRequest = new SetExpressCheckoutRequestType()
                {
                    SetExpressCheckoutRequestDetails = new SetExpressCheckoutRequestDetailsType()
                    {
                        ReturnURL = returnurl,
                        CancelURL = cancelurl,
                        BuyerEmail = CustomerHandle.GetIdentityName(),
                        PaymentDetails = new PaymentDetailsType[]
                        {
                            new PaymentDetailsType()
                            {
                                OrderTotal=OrderToal,
                                PaymentDetailsItem=new PaymentDetailsItemType[]
                                {
                                    new PaymentDetailsItemType
                                    {
                                        Amount = OrderToal,
                                        Number = "",
                                        Quantity = "1",
                                        Name =string.Format("#{0}#",orderNum)
                                    }
                                },
                                PaymentAction=PaymentActionCodeType.Sale,
                                ShipToAddress=new AddressType
                                {
                                    Name=string.Format("{0} {1}",shippingaddr.FirstName,shippingaddr.LastName),
                                    Street1=shippingaddr.ADD1,
                                    Street2=shippingaddr.ADD2,
                                    CityName=shippingaddr.City,
                                    StateOrProvince=shippingaddr.State,
                                    PostalCode=shippingaddr.Postcode,
                                    //Country=countrycode,
                                    /*paypal文档中说Country是必要的*/
                                    Country=CountryCodeType.NL,
                                    CountryName="Netherlands",
                                    
                                    Phone=shippingaddr.Postcode
                                }
                            }
                        },
                        AllowNote = "0",
                        cppheaderimage = ConfigurationManager.AppSettings["LOGOURL"],
                        BrandName = ConfigurationManager.AppSettings["BrandName"],
                        NoShipping = "0",
                        /*此外设置为1总是返回错误,设置为0无错误*/
                        AddressOverride = "1",
                        ReqConfirmShipping = "0"
                    },
                    Version = API_VERSION
                }
            });