Skype实时媒体机器人挂断电话

Question

我构建并部署了Skype实时媒体bot https://docs.microsoft.com/en-us/azure/bot-service/dotnet/bot-builder-dotnet-real-time-audio-video-call-overview?view=azure-bot-service-3.0

Bot接受电话后会立即挂起电话。日志只剩下跟踪（没有错误）：

EventName="MessageEvent" Message="[d013fb23-e4fd-41a4-ae00-a6d10d844fb5 SendAsync,LoggingMessageHandler.cs(139)] || correlationId=d013fb23-e4fd-41a4-ae00-a6d10d844fb5 || statuscode=Accepted || local.msgid=9b27e78c-c8d4-4abc-8710-d45b960b3158 ||
Response to incoming:: POST https://*******/api/calling/call
202 Accepted
Connection: close
X-Microsoft-Skype-Chain-ID: d013fb23-e4fd-41a4-ae00-a6d10d844fb5
Content-Type: text/plain; charset=utf-8
{
  "notificationSubscriptions": [
    "callStateChange"
  ],
  "links": {
    "callback": "https://********:10100/api/calling/callback/",
    "notification": "https://*********:10100/api/calling/notification/"
  },
  "actions": [
    {
      "operationId": "277bd339-88dd-4830-ae76-396558897f1d",
      "action": "answerAppHostedMedia",
      "mediaConfiguration": {
        "mpUri": "net.tcp://**********:20100/MediaProcessor",
        "audioRenderContexts": [
          "9585de0f-d833-4fb9-be92-834e7d48182b"
        ],
        "videoRenderContexts": [
          "ac210c59-c1cf-474e-a0c3-4be29f3a6f03"
        ],
        "audioSourceContexts": [
          "1462102d-5a43-4a93-b553-c46c82734fe9"
        ],
        "videoSourceContexts": [
          "49c4c0c5-9dcc-405d-9df1-ec8b85e8fea3"
        ],
        "dataRenderContexts": null,
        "dataSourceContexts": null,
        "supportedAudioFormat": "Pcm16K",
        "videoSinkEncodingFormats": [
          "Yuv"
        ],
        "mpMediaSessionId": "eeaf9871-f73d-4949-8b0a-b48d0fc4554b",
        "regionAffinity": null,
        "skypeMediaBotsVersion": "1.9.0.0001",
        "mediaStackVersion": "2018.23.1.3",
        "mpVersion": "7.2.0.2146"
      }
    }
  ],
  "appState": "453da625-6a67-405b-9da1-e0cb74f88221"
}
$$END$$" TraceSource="FrontEnd"

如果您遇到类似的问题，能否请您帮助我确定为什么bot（或skype）在我拨打电话后挂断电话？ 谢谢！