Thermostat displays E43 and shows no internet connection

Note: The thermostat is connected to the router but the router has no internet access.

• Check other devices: Verify if phones or computers on the same Wi‑Fi can access the internet. If not, the issue is with the ISP or router.
• Inspect modem and router: Ensure all cables are firmly connected. Check that the modem’s online/Internet light is solid and the router’s WAN/Internet light is on.
• Restart modem and router: Unplug both for 30 seconds, plug in the modem first, wait for full sync, then plug in the router.
• Check ISP status: Contact your internet provider or check their status page for outages.
• Public or guest networks: If using a guest or public Wi‑Fi that requires a web login, the thermostat may not be able to authenticate. Use a standard home network instead.
• After internet is restored: The E43 code should clear automatically once the router regains internet access.