I’m getting very frustrated with this situation at this time. I have 4 google mesh, Nest doorbell, Yale lock with nest connect, 4 cameras, 4 google Dots, google Hub, 2 nest thermostats, google comcast and 4 nest protects I’m probably missing the rest. I’m really thinking about switching to something else because of this issue. I upgraded my WiFi and the nest connect and 4 protects won’t connect. I’ve restarted, Wi-Fi and factory reset and several other things and nothing,
Thanks for reaching out here in the Community. I know you've been having a lot of trouble because of this and that is not the experience we want you to have. A few reminders for the Nest Protect. It can only connect to the 2.4GHz Wi-Fi network and can only set up to your Nest app. So if your new Wi-Fi router only broadcasts the 5GHz network, then I would suggest you to its setting and check if you can enable the 2.4GHz or contact its manufacturer and ask for assistance on how can you can enable it. Let us know how it goes.