I am sorry to hear that you are having this issue with multiple cameras! Have you tried to restart all of them? And restart your wifi? Restarting and factory resetting your Google Nest camera or doorbell will have different results:
Restart: Keeps all your settings, and it should reconnect to the same Wi-Fi network. This is helpful if it ever becomes frozen, has trouble reconnecting to the internet, or isn't working normally.
Factory reset: Erases all your settings and options, and restores its factory default settings. It will not automatically reconnect to Wi-Fi and you'll need to set it up again.
You can find this information, plus additional information on this process here. Please let me know if you have further questions.