This was my exact problem the first time and I did perform a factory
reset on the original thermostat and then successfully added the second
thermostat immediately thereafter. For subsequent thermostats, though, I
did not need to do another reset tho...
I was able to fix this problem and now have 5 thermostats running fine.
I spoke to support and walked through it. Took awhile but we learned the
glitch. Essentially after the first thermostat links to the wifi network
every subsequent Nest needs to b...