@Mkafi
The most likely reason for getting a username/password error when trying to sign onto the Google Nest app AND not getting a password reset email is that you are somehow inadvertently using a different email than you've used in the past.
If that is NOT the case, you could try contacting Support to see if something else is going on:
1. Go to https://support.google.com/googlenest/gethelp.
2. Select a category/product family, and type in a brief description of the issue, then click "Next".
3. Click "Other", then click "Next step".
4. Under "Resources", just click "Next step". (Clicking one of the listed links will bring up a Help page page.)
5. Under "Contact options", choose to get a phone call or chat with the team, depending on availability in your country.
