A lot of Android wear users have been complaining about the voice related issues with the Google Assistant. Now, according to Google product community manager, the issues with voice seem to have been fixed and have also released an update to Google app in the Play Store (version 7.8).
Follow the steps above to update the Google app on your wear.
You can also follow the full discussion on Google product forums by visiting the link below.
More information on Android Wear.
