Google has finally addressed a longstanding issue on Android Auto that prevents users from using Google Assistant on the platform. All you need to do is update the Google app on your phones to make things return to normal. A bug has left Google Assistant unusable on Android Auto with the error "Internet connection is not stable" continually appearing.
Users have been reporting this issue since early 2020, and now the company finally has a fix for it. Google tried to remedy it earlier, but the problem returned. Now, everything is said to be back to normal. Google hasn't specified what version fixes this problem, but installing the latest version of the Google app (version 11.14.8) should fix it.
Source: Auto Evolution