@Outback
I'm just another Google Nest customer and am not clear what's all happened in your case, but let me try a few comments. If you're logging onto the Google Nest app AND the Google Home app with the same gmail account and password, and the cameras are all in the same "home", you see your older cameras automatically in the Google Home app,
I log into the Google Nest app with the same gmail account and password I use to log into the Google Home app. I migrated my Nest account to a Google account about two years ago , after they pestered us to do so (https://support.google.com/googlenest/answer/9297676?hl=en&co=GENIE.Platform%3DiOS&oco=0#migrate-nes...).
I can't remember the details, but I did NOT "add" my existing cameras to the Google Home app. Once I migrated, the cameras simply appeared in the Google Home app. All of our cameras appear in both apps, but while we can see the camera feeds in the Google Home app, we can ONLY administer our older cameras and view their history in the Google Nest app.
When we bought a new Google Nest Camera (Battery) last fall, we discovered we had to add it in the Google Home app, and it does NOT appear in the Google Nest app. When we bought a new Google Nest Hello Doorbell, we added it in the Google Nest app because older devices still get added in the Google Nest app, but once we added it, the doorbell then appeared automatically in the Google Home app along with our other cameras.
Maybe this will give you some clues on how to proceed, depending on what you've already done.
(By the way, I hate this 2-app approach that Google Nest contrived. For what it's worth, you can find their rationale in this blog in this forum: https://www.googlenestcommunity.com/t5/Blog/Message-from-our-GM-Updates-for-our-Nest-customers/ba-p/....)
