沙箱环境下，客户端发起道具直购requestMidasPaymentGameItem时，总是返回-15014paysig签名错误，签名算法没问题，,客户端收到paySig和SignData也和服务器下发的一致，参数如下

sigData={"buyQuantity":10,"currencyType":"CNY","env":1,"goodsPrice":100,"mode":"goods","offerId":"xxxxxxxx","productId":"xxx","zoneId":"xxx"}

米大师appkey：xxxxxxxxx

needMsg = "requestMidasPaymentGameItem&{"buyQuantity":10,"currencyType":"CNY","env":1,"goodsPrice":100,"mode":"goods","offerId":"xxxxxxxx","productId":"xxx","zoneId":"xxx"}"

是sigData哪个参数填的不对吗 求解