I have 2 Nest Gen 3 thermostats that have worked fine through the Nest binding (SDM). A few days ago one of the thermostats stopped being updated and the logs showed errors “openhab nest sdm api error device … not found”. I tried restarting, removing the thing and scanning for new devices. Unfortunately the device was not detected.
Looking in the Nest app (that still works fine) I noticed that very recently the firmware was updated from version 5.9.5-2 (dated Mar 19, 2022) to 6.4-5 (dated Jun 17, 2025). The thermostat that is still working with the binding is still at 5.9.5-2.
I switched on debug logging but could not get any clues on the missing thermostat. It clearly finds only one when calling:
I did some further reading and found similar issues reported by HA users who had their thermostat automatically updated to 6.4-5. For some of them it started working again, not for me unfortunately.
In the end I decided to start from scratch and follow the Nest binding documentation to set everything up again. Things have slightly changed in the Google Cloud Console. Initially I could not get pub/sub working, following error is shown when adding a pub/sub topic to the project:
Device Access service cannot publish messages into the specified PubSub topic. Verify that sdm-publisher@googlegroups.com has the PubSub Publisher role in the PubSub topic. Make sure you have followed the prerequisites in the documentation ([link](https://developers.google.com/nest/device-access/subscribe-to-events))
Trick here is to add a Principal (sdm-publisher@googlegroups.com) to the Topics (tab), not the Subscriptions (tab), within the Google Pub/Sub API configuration page. On the Topics tab, click the 3 dot menu next to the topic you created, then select View Permissions. A sidebar menu will popup where you can add a Principal and give it the Pub/Sub Publisher role. You do not need any Principal configured on the subscription-level, only the topic-level.
Has been a while since I had to go through the Google Cloud Console “labyrinth”, and probably I will have to do this again when the other Thermostat decides to update itself. I noticed that the newer firmware (after years of Google not fixing any of the issues with the thermostat) has some additional features when accessed through the Google Home app.
