@Edhead
It's possible something odd is going on in your case, but the most common reason for not being able to sign on AND not getting a password reset is if you are somehow inadvertently using the wrong username--a username that's not in Google Nest's database of customers, so they can't send you a reset email.
This is Google Nest's Help topic on Nest Account password reset. There's a link there for contacting Support.
https://support.google.com/googlenest/answer/10371718
