I'm following the guide for building a basic smarthome device as per: https://developers.home.google.com/codelabs/smarthome-washer
However, the fakeauth/login is failing. When I select the "Link this service to Google" button that appears (as part of the process to add the Action) from the Google Home app on my phone, the process abruptly ends with the toast message "Could not reach [test]. Please try again"
I tried running it outside of the Google Home app and a "return to App" link is expected. (The backend is NOT running Firebase, it's using Express). When reaching this page by manually feeding the redirect URL to the mobile browser, the "return to App" link briefly causes some other App to open up before immediately closing and returning to the browser. The link is unsuccessful.