Last thing to do is to Create a Project in Nest Device Console. Click 1.
After registration and paying the 5$ fee you can access the Device Acces Console to create a project.
Give it a Name and click Next
You are now asked for the OAuth Client ID created earlier. This ID is on your Clipboard!
Next Enable Pub/Sub events, these events are pushed to a Homey webhook.
Click Create Project.
Next on the Project screen, click the copy to clipboard icon, to get the Project ID you need to paste in the Homey App.
The Homey app now shows the Login button. Click it and it will guide you through the request for device access authorisations and it will ask for some other authorizations as well. Make sure that you enable all required devices and functions (all must be selected). The app is marked as unsave as it is not verified by Google. So just select advanced settings to continue. DO NOT USE BACK TO SAFETY , the app will not function if you do so.
If all finished you are good to add your Nest devices.