@Htapal
The reference to selecting the "WiFi" option in the Google Home app does not apply to your situation. It applies if you have Google Wi-Fi routers and wish to update the Wi-Fi settings on the Google Wi-Fi routers.
Google Nest does not make it easy to change Wi-Fi settings on its devices, such as cameras and Nest Hubs. As a result, their recommendation when changing routers/modems "is to update your home network so that the network name (SSID) and password are the same as before."
https://support.google.com/googlenest/answer/9223711?hl=en#zippy=%2Ctry-the-same-network-name-and-pa...
If you can't manage that, then you're supposed to remove your camera or doorbell from the Google Home app and do a factory reset while you are still on your old Wi-Fi network. (See the same page above.)
If you've already changed your Wi-Fi network, then things get messy. Some customers are able to do a factory reset (https://support.google.com/googlenest/answer/9252162#factory-reset&zippy=%2Cnest-doorbell-battery) and then do a reinstall.
Others find that they cannot proceed and end up contacting Google Nest Support (https://support.google.com/googlenest/gethelp) and hope they get someone knowledgeable who can guide them out of this dilemma.
(I didn't invent the process and am not a expert; I'm just another Google Nest customer.)
