Just as a heads up to anyone else that runs into this issue, my badnest integration stopped working. After a restart of HASS, it notified me that the issue was my access token.
I went back through the setup of this integration and noticed I couldn’t find my cookie starting with “OCAK=…”.
I did however find my access cookie starting with “HSID=…”. This new cookie was much longer and had more fields and values included in it. Updating my cookie to this new value worked flawlessly for me and I have access to my thermostat again.
Don’t know if google updated their authentication today, or if it’s just an issue with me. Hope this helps someone else.