When you have a smart home integration with a device manufacturer/company there is a account linking process between Google and that Company on the Google Account. The Google system stores access tokens to interact with these services on your behalf ( For eg. When you give a Google Assistant command to interact with your devices ). Occasionally if this account linking is broken or the service side company invalidates this token (sometimes by mistake) Google Home may respond to your smart home by something went wrong or please re-link your account. For those cases try unlinking your account going through disconnecting devices/services documentation
