You cannot reset the passcode if the device is not in the app any longer. By then, I had already removed the Nest thermostat from the Nest app which made the Nest basically useless at this point. When I put the Nest back onto the new home’s wall, I was greeted with a 4 digit passcode screen which I did not remember setting. Recently, I moved to another home and took our old Nest thermostat with us. If this happens, you are not out of luck however, it’s not the easiest process to get the pin code reset. The downside to this is that if you set one of these codes up on your Nest thermostat, there is a possibility that you forget the code–or–you remove the Nest device from your Nest app before resetting the passcode. There are times when you set up a Nest thermostat with a security password, whether you are a parent trying to keep the kids out, or, you are a landlord and don’t want renters to play around with the Nest.
