I am having the same problem. Cant add Nest in the home app, like i have fx Sonos. Plus the new outdoorcamera i bought, wont show in Nest app, so i am forced to use both app´s now.
Epic fail Google...smh.
Thinking about make a change over to another brand, for better and more userfriendly app/connectivity
Stupidly, even trying to sign in with Google on the Nest "works with" link doesn't work- because Google didn't update to their own standards. Gives "error: 400 redirect_uri_mismatch" with further detail "you can't sign into this app because it doesn't comply with Google's OAuth 2.0 policy" 🙄