I'm taking a guess here but was this camera ever loaded into the NEST APP? If so you probably have to go back to that app and REMOVE it rather than trying to remove it from GOOGLE HOME app?
To delete a camera from the Google Home app,open the app, tap on the camera, go to its settings (the gear icon), and select "Remove device". If this doesn't work, try using the "Settings" > "Rooms and groups" path, or try creating a new home, moving the device to it, and then deleting the new home. You can also try refreshing the app or creating a new home and moving the device to it before deleting the old room.
Standard removal
Open the Google Home app.
Tap on your camera's tile or go to "Home" and then "Cameras".
Tap the gear icon for Settings in the top right corner.
Scroll down and tap Remove device.
Confirm the removal.
Alternative removal methods
Through Rooms and groups: Go to Settings > Rooms and groups, select the room the camera is in, tap the device, and choose Remove device.
Using Assistant settings: Tap your profile icon, go to Assistant settings, then Devices, select the camera, and tap Unlink this device.
Create a new home: If the device is still there, create a new home, add the camera to it, and then delete the new home. This can help clear out old or offline devices.
If the device is still not deleting
Check the manufacturer's app: For devices that are not Matter-enabled, you may need to remove them from the original manufacturer's app.
Update the app: Make sure your Google Home app is updated to the latest version.
Restart your phone: A simple restart can often resolve syncing issues.
