[Update]
Google has changed the original authenication method. Only the Google Account Cookie Method will work. Use the incognito method described here.
NOTE: I cannot confirm if this is going to work with the homebridge-nest plug-in. After many failed attempts, I ended up having success with a HACS integration for Home Assistant that is based on the homebridge-nest plugin (specifically version 0.3.12 of the Nest Protect integration for Home Assistant is what is working for me).
If you are running Home Assistant with Home Assistant Device Bridge, I highly recommend this integration as it's easier to work with since no virtual devices and HomeKit automations are required, plus it exposes control over the Nest Protect settings that the homebridge-nest plugin does not.
