Sorry to hear that. While we don't support Google Chat issues, we can point you in the right direction. Our friends at Google Chat Help Community are the perfect folks to help you with it.
As for my advice, please make sure that your device is connected to the network and that you are using the right account to reply to your messages. Check this out to know more about Google Chat.
If you have any new issues, updates or just a discussion topic about the Google Home/Nest devices, feel free to start a new thread in the Community.