We are trying to provide updates about a background to user (in MS Teams app). The code used to updateActivity is as follows,
this.adapter.continueConversation(conversationReference, async (context) => {
      let activity = MessageFactory.attachment(CardFactory.adaptiveCard(card));
      activity.id = request.id;
      activity.serviceUrl = request.serviceUrl;
      activity.conversation = request.conversation;
      await context.updateActivity(activity);
    });
Error: Unknown
    at new RestError (/usr/src/app/node_modules/@azure/ms-rest-js/dist/msRest.node.js:1397:28)
    at /usr/src/app/node_modules/@azure/ms-rest-js/dist/msRest.node.js:1849:37
    at process._tickCallback (internal/process/next_tick.js:68:7)
Note that sendActivity works correctly. The error 'Unknown' is not really helpful though.