If you are accessing the Google Nest app and the Google Home app with the same Google account and if your cameras are all in the same Google Nest "home/structure", then you should see both cameras in the Google Home app, but you can only administer your older camera in the Google Nest app.
Google Nest has just made available a new website in "preview" form where we can see all our cameras: https://home.google.com.
The new site is explained here: https://www.googlenestcommunity.com/t5/Blog/Check-out-your-cameras-on-the-web-with-Google-Home/ba-p/...
Just checking in to see how the conversation is going. Please let us know if you have any further questions or concerns. We'll leave this thread open for a little longer for follow-up questions and concerns.