In my case, there have been no changes to the Wi-Fi. In the most recent case, the Nest had upgraded from 1.1-9 to 1.1-11 around the same time as this "Wi-Fi connected/Server not-connected" event.
The problem was noticed because the Home App listed "ERROR!" for the Themostat and I was unable to change the heat setting remotely nor tell the temperature or anything.
When I arrived at the home, the Nest said it was connected to Wi-Fi, however when I selected the "Check Nest Server", it gave me "Not connected" and code g.co/nest/m22. However, all my other Wi-Fi devices (Roku, mobile phone, laptop) were all connected to the same Wi-Fi and able to access anything on the internet.
I do suspect that the Wi-Fi may have had an intermittent upstream outage prior to this problem occurring. The internet service at this location does occasionally have an outage. My hunch is that there may be an issue with the Nest retrying to connect to the server if the Wi-Fi connection stays connected. This should be an easy scenario to reproduce, however I do not the ability to experiment with the internet connection upstream of the Wi-Fi AP at that location and I do not have another Nest that I could experiment with.
The only way I have to recover from this scenario appears to be restarting the Nest. Note: I can not reboot the Wi-Fi AP since it is a community AP managed by the Internet Provider (Startouch).
Also, I do not have access to a mobile hotspot device to try instead of using the Internet Provider's Wi-Fi AP (it is literally my only option for internet at that location).
It does seem like this would be a scenario that is easy to setup and test for in a controlled environment, but I do not have an extra Nest, extra Wi-Fi routers, nor the extra time to do that.
