//Publishing the topic
                        snsClient.Publish(new PublishRequest
                        {
                            Subject = Constants.SNSTopicMessage,Message = snsMessageObj.ToString(),TopicArn = Settings.TopicArn
                        });

我收到以下错误：

The underlying connection was closed: A connection that was expected
to be kept alive was closed by the server.

这是详细错误的屏幕截图：

但无法知道如何解决这个问题.任何提示或链接都会有所帮助.