Hey there gemgal72,
Sorry to hear about the error message you're running into when you try to set up your new Nest device, I understand it can be confusing, but I'm happy to look into this for you.
Are you using a school or business email?
G Suite accounts are accounts set up by businesses or organizations to access different Google business productivity tools. At this time, you can’t use a G Suite account because the account data is managed by your organization. We recommend migrating your Nest Account to a personal Google Account. If you don’t have one, create a new Google Account.
It is also not possible to unlink a Google Account and Nest Account that have already been linked to each other. You can also reach to support by following this link.
Please let me know if you have any further questions or concerns.