我使用谷歌钱包使用javascript和谷歌应用引擎的数字商品。当我的应用程序调用buy（）函数时，我会在演示中看到预期的屏幕，但随后它会超时并给出错误消息。消息是Uh oh. There was a problem. We couldn't start your purchase because of a technical issue. Details of the problem below: There is an error in the setup for your purchase. Please contact the merchant about this issue.
谁能给我一个关于问题源于何处的线索？