调用支付宝支付的时候，总是显示系统繁忙，怎么办

私钥生成了，也转成了pkc8格式了，但是进入支付宝页面后，总是提示系统繁忙
代码如下：

-(void)jumpToAlipay{
    /*
     *生成订单信息及签名
     */
    //将商品信息赋予AlixPayOrder的成员变量
    Alipay_Order *order = [[Alipay_Order alloc] init];
    order.partner = ALIPAY_PARTNER;
    order.seller = ALIPAY_SELLER;
    order.tradeNO = [self generateTradeNO]; //订单ID（由商家自行制定）
    order.productName = _itemContentArr[0]; //商品标题
    order.productDescription = _itemContentArr[1]; //商品描述
    order.amount = [NSString stringWithFormat:@"%@",_price]; //商品价格
    order.notifyURL =  @"http://www.xxx.com"; //回调URL

    order.service = @"mobile.securitypay.pay";
    order.paymentType = @"1";
    order.inputCharset = @"utf-8";
    order.itBPay = @"30m";
    order.showUrl = @"m.alipay.com";

    //应用注册scheme,在AlixPayDemo-Info.plist定义URL types
    NSString *appScheme = @"screem";

    //将商品信息拼接成字符串
    NSString *orderSpec = [order description];
    //    NSLog(@"orderSpec = %@",orderSpec);
    //    NSLog(@"privatekey:%@",ALIPAY_PRIVARYKEY);
    //获取私钥并将商户信息签名,外部商户可以根据情况存放私钥和签名,只需要遵循RSA签名规范,并将签名字符串base64编码和UrlEncode
    id<DataSigner> signer = CreateRSADataSigner(ALIPAY_PRIVARYKEY);
    NSString *signedString = [signer signString:orderSpec];
    NSLog(@"singedstr:%@",signedString);
    //将签名成功字符串格式化为订单字符串,请严格按照该格式
    NSString *orderString = nil;
    if (signedString != nil) {
        orderString = [NSString stringWithFormat:@"%@&sign=\"%@\"&sign_type=\"%@\"",
                       orderSpec, signedString, @"RSA"];
        NSLog(@"orderstr:%@",orderString);
        [[AlipaySDK defaultService] payOrder:orderString fromScheme:appScheme callback:^(NSDictionary *resultDic) {
            NSLog(@"reslut = %@",resultDic);
        }];
    }
}

各个参数也有值 ：partner="20880211244xxxxx"&seller_id="310180xxxx@qq.com"&out_trade_no="ASTZWWVG2RH044L"&subject="乐币"&body="虚拟币"&total_fee="1"&notify_url="http://www.xxx.com"&service="mobile.securitypay.pay"&payment_type="1"&_input_charset="utf-8"&it_b_pay="30m"&show_url="m.alipay.com"&sign="nN6V9qfoM8PXrnoNgTlkfI1qQ1T3t6tPQncGC4WockCuX4ceCiko7KbUIqxDe0jzhxv39BsvvqHfHdX9%2FpnbdlYc0ax28TakyUZXJwPaTCxIYDFsHzdObF8f%2BVW516ry6ZKE9DAy9ZxAxxxxxxxxxxxxFQzUGvqlT%2BVRLeAYtmP98g%3D"&sign_type="RSA"