Having decided to rebuild a fresh production HA to replace my current unit from 2021, I need to connect my Nest Thermostat to the new HA. I have the Nest unit functioning in my old version and the was imported from the yaml config.
In the new HA follow the guide and get to the final stage and HA responds with "unknown error talking to Cloud Pub/Sub, see logs.
The logs are giving:
> Logger: homeassistant.components.nest.config_flow
> Source: components/nest/config_flow.py:295
> integration: Google Nest ([documentation](https://www.home-assistant.io/integrations/nest), [issues](https://github.com/home-assistant/core/issues?q=is%3Aissue+is%3Aopen+label%3A%22integration%3A+nest%22))
> First occurred: 17:18:20 (3 occurrences)
> Last logged: 18:51:25
>
> Error listing eligible Pub/Sub topics: Error while listing existing cloud console topics
Is this a common error and has anyone got any advise on what to look at. I’ve gone over the install guide a number of times and cant see what i am missing.
2026-02-09 20:03:39.700 INFO (MainThread) [homeassistant.components.nest.config_flow] Successfully authenticated
2026-02-09 20:03:39.774 DEBUG (MainThread) [google_nest_sdm.admin_client] SDM topic exists but we do not have permission to access it (expected)
2026-02-09 20:03:39.776 INFO (MainThread) [google_nest_sdm.admin_client] Unexpected error listing topics: Forbidden response from API (403): PERMISSION_DENIED (403): Cloud Pub/Sub API has not been used in project xxxbefore or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/pubsub.googleapis.com/overview?project=xxxxthen retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry.
Error details: ([{'@type': 'type.googleapis.com/google.rpc.ErrorInfo', 'reason': 'SERVICE_DISABLED', 'domain': 'googleapis.com', 'metadata': {'serviceTitle': 'Cloud Pub/Sub API', 'service': 'pubsub.googleapis.com', 'activationUrl': 'https://console.developers.google.com/apis/api/pubsub.googleapis.com/overview?project=xxxxx', 'containerInfo': 'xxxxx', 'consumer': 'projects/421630283548'}}, {'@type': 'type.googleapis.com/google.rpc.LocalizedMessage', 'locale': 'en-US', 'message': 'Cloud Pub/Sub API has not been used in project xxxxx before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/pubsub.googleapis.com/overview?project=xxxxx then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry.'}, {'@type': 'type.googleapis.com/google.rpc.Help', 'links': [{'description': 'Google developers console API activation', 'url': 'https://console.developers.google.com/apis/api/pubsub.googleapis.com/overview?project=xxxxx'}]}])
2026-02-09 20:03:39.778 ERROR (MainThread) [homeassistant.components.nest.config_flow] Error listing eligible Pub/Sub topics: Error while listing existing cloud console topics
Pub/Sub API applied
New error:
2026-02-09 20:09:28.064 INFO (MainThread) [google_nest_sdm.admin_client] Unexpected error listing topics: Not Found response from API (404): NOT_FOUND (404): Requested project not found or user does not have access to it (project=xxxx). Make sure to specify the unique project identifier and not the Google Cloud Console display name.
2026-02-09 20:09:28.065 ERROR (MainThread) [homeassistant.components.nest.config_flow] Error listing eligible Pub/Sub topics: Error while listing existing cloud console topics
2026-02-09 20:09:28.460 DEBUG (MainThread) [google_nest_sdm.admin_client] SDM topic does not exist, proceeding to check cloud projects
OK . Rebuilt the nest API and ap. Followed the logs and got it working 
