Smart thermostat app reports 'Boiler Offline' or 'Device Offline'; the thermostat appears normal but cannot control the boiler.

Safety first: If the gateway is mains-powered, switch off at the socket before unplugging cables.

• Check gateway LEDs: Inspect the Worcester Bosch internet gateway or smart controller. Confirm power, network, and status LEDs are lit as per the manual.
• Restart gateway: Power off the gateway for 30 seconds, then power back on. Wait several minutes for it to reconnect.
• Check network cable/Wi-Fi: If using Ethernet, ensure the cable is firmly plugged into both the router and gateway. If using Wi-Fi, verify the SSID and password are still valid and that the router is broadcasting.
• Check app status: Log out and back into the app. Check if Worcester Bosch reports any service outages on their support site.
• If still offline: The gateway or receiver may have failed. Contact Worcester Bosch support for replacement options.