NEST Connectivity Issues Solved
I have two NEST thermostats, one v1 and one v2. The v1 had been ticking along fine until about July 2014 when I began to experience connectivity problems. More specifically, the thermostat itself would say that it was connected properly, but the NEST browser and mobile apps would show it as offline. I tried all the usual fixes: reboot, restart, reset, both (router and NEST), static ip, DHCP Leasetime tweaks, etc. Long story short, nothing I did solved the connectivity issues.
As it turned out, I was reconfiguring my home network and decided to change my main router from a Netgear WNDR4500 to an ASUS RT-AC68U. This change has resolved all my NEST connectivity issues. NEST Connectivity Issues Solved ! Both my NEST thermostats are fully connected and accessible any time I check them. It turns out that the RT-AC68U has many other useful features such as 6 definable guest networks, dual WAN interfaces, and a VPN server.
When I installed my v2 NEST in another part of my house, I made sure that I had the common wire available to prevent any charging/voltage issues, and there have been none. There have been numerous posts about this, and on my system, the common wire is needed.
To add another layer of complexity, I recently decided to implement a UTM (Unified Threat Management) solution for my home network using the software from Sophos and hardware from Dell . It required some tweaking of the UTM in order to get the NEST thermostats to be properly connected. This included static ip addresses for each NEST, and some additional network and firewall rules opening various ports.
If you are having these type of intermittent, seemingly unsolvable connectivity issues, and you have exhausted all other avenues, then I would suggest that you try another brand of router.
Update: I continue to have no connectivity issues several weeks into this new hardware setup (as of October 24, 2014)