Why can't step into promise success handling logic

Question

I follow this sample [https://github.com/OfficeDev/Microsoft-Teams-Samples/tree/main/samples/tab-external-auth

](https://github.com/OfficeDev/Microsoft-Teams-Samples/tree/main/samples/tab-external-auth

), development my own Tab web application's external-auth, I can popup login page, but after login, I can't step into this code segment

authentication.authenticate({
      url: ``,
      isExternal: true
    }).then((result) => {
      //can't step into here
    }).catch((reason) => {
      console.log("failed" + reason);
      reject(reason);
    })