OK I understand, and that's common, try restart, by pressing the display against the wall until the house comes back on. Then see if the error comes back. You can also try to go into Software update, and try to update the software. You will not be able to obvioulsy with the W5 fault. Try also reset of the network in the Reset menu, try these methods a few times. Factory reset is not always the best, as sometimes it clears the error code, as it has with yours.
You are trying ways to force the error back on the screen.
Nest are really helpful, but without proof, sadly their hands are tied.
By the way, was your thermostat logged into your account before this happened?
