So, in theory, Google Assistant just goes back to sleep after waking it with the “OK, Google” phrase, and no workaround seems to be bringing it back. I came across a similar thread on Google’s forums, and the original post seems to indicate the problem was first reported in October this year. However, not everybody appears to be impacted, though the affected users explain that Google Assistant also stops working after recognizing the wake-up phrase. In all cases, they complain that sending a text or making a call is pretty much impossible when the car is moving.
However, I recently noticed that getting directions from Google Maps is suddenly much more difficult on Android Auto, especially when in motion. So naturally, voice commands are the only supported input method on Android Auto while driving, and this happens for an obvious reason. But the voice commands themselves appear to be broken after a recent update, with Google Assistant no longer doing anything after previously responding to the “OK, Google” wake-up phrase. I first noticed this problem when trying to set up Google Maps, but then I discovered the same thing happens with pretty much all commands.
No workaround is known to exist, and more unexpected is that not even downgrading to an earlier version of Android Auto or the Google app seems to restore the expected behavior. Google is yet to acknowledge the problem, so for now, you’re all alone in your quest to find a fix if the same thing happens to you too.