我遇到了同样的问题，开始活动结果一直返回RESULT_CANCELED和errorCode16.问题是我在Google Cloud Platform Console中的客户端配置.我正在使用常规的调试和发布api密钥.当我将 Web应用程序用作Google控制台配置时，结果返回OK.

I had the same problem, start activity result kept coming back with RESULT_CANCELED and errorCode 16. The problem was my client configuration in Google Cloud Platform Console. I was using the regular debug and release api key. The result came back OK when I used web application as my Google Console configuration.

希望有帮助.