Nest thermostat: W2: Failed to connect (router security)
Failed to connect: your Wi-Fi router may have security settings turned on that stop the thermostat connecting.
Applies to: All Nest thermostats. What you see: a code and words.
What Google says to do
- Google says to find the thermostat’s MAC address and add it to your router’s whitelist (its list of allowed devices).
The maker puts this down to Wi-Fi or the network. If the problem is the router itself, its own lights are explained on the router and broadband hub lights page.
Source
Google’s own help page, read on the date shown.
- Google Nest Help: Troubleshoot Nest thermostat help codes — Nest Learning Thermostat (1st to 4th gen), Nest Thermostat E and Nest Thermostat; H codes only where a Heat Link is installed. support.google.com Checked 2026-09-29.