@Guytou
Did you remove your camera from the Google Home app while you were still on your old Wi-Fi network, and then, if necessary, perform a factory reset before trying to reinstall it on your new Wi-Fi network?
https://support.google.com/googlenest/answer/9223711
https://support.google.com/googlenest/answer/9252162
Another possibility--Google Nest's first recommendation--is to set the network name (SSID) and password on your new router/modem to the same values used on your old router/modem. We did this a couple of years ago, and did not have to update any of our Google Nest devices.
