2 weeks ago
I purchased a Hub Max from an individual and have not been able to set it up with my home because it is still showing as linked to the previous owner's home. I am in contact with the prior owner and he indicated it is no longer connected to him.
2 weeks ago
If you're getting a message that your Nest Hub Max is connected to another account, then the previous owner did NOT remove the Nest Hub Max from their Google Home app while they were still on their old Wi-Fi network, and perform a factory reset.
You could try a "factory reset" (not just a "restart"):
https://support.google.com/googlenest/answer/7073477
I don't think Google Nest Support would contact the previous owner.