botbuilder-js: Oauth prompt fails to start

After following the guide on using the OAuthPrompt dialog from botbuilder-dialogsand it seems like all requests related to retrieving the user token for a connection are failing with a status code of 401, thus the prompt never makes it past the stage of trying to check if we have a token before starting the dialog prompt for the oauth connection.

I have properly configured appId and appPassword and am able to successfully use other api methods like getActivityMembers from the BotFrameworkAdapter adapter instance. However I noticed that when the SDK tries to make the request to check if we have a token for a user/connection it does not send any authorization header, thus it makes sense that the request fails with a 401 status code.

Here is the full error message + stack trace:

{ Error
    at new RestError (/Users/agonbina/Gameon/bot/node_modules/ms-rest-js/lib/restError.ts:13:5)
    at OAuthApiClient.<anonymous> (/Users/agonbina/Gameon/bot/node_modules/botframework-connector/src/oAuthApiClient.ts:83:21)
    at Generator.next (<anonymous>)
    at fulfilled (/Users/agonbina/Gameon/bot/node_modules/botframework-connector/lib/oAuthApiClient.js:11:58)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:118:7)
  code: undefined,
  statusCode: 401,
  request:
   { headers:
      { 'Content-Type': 'application/json; charset=utf-8',
        'User-Agent': 'Node/v9.10.1 (x64-Darwin-16.7.0) ms-rest-js/0.1.0 botframework-connector/4.0.0 Microsoft-BotFramework/3.1 (BotBuilder JS/4.0.0-preview1.2) Azure-SDK-For-Node',
        cookie: '' },
     rawResponse: false,
     url: 'https://api.botframework.com/api/usertoken/GetToken?userId=default-user&connectionName=Facebook',
     method: 'GET' },
  response:
   { body:
      PassThrough {
        _readableState: [ReadableState],
        readable: false,
        domain: null,
        _events: [Object],
        _eventsCount: 4,
        _maxListeners: undefined,
        _writableState: [WritableState],
        writable: false,
        allowHalfOpen: true,
        _transformState: [Object] },
     headers: Headers { _headers: [Object] },
     status: 401 },
  body: undefined }

Happy to provide more information if necessary, otherwise this should be simple to re-produce by following the example provided in the docs for OAuthPrompt.