Wiser Room Thermostat shows E12 and the app reports over-temperature protection; heating is disabled.

Safety: Do not attempt to cool the thermostat rapidly with water or ice; avoid condensation.

• Check installation location: If the thermostat is above a radiator, on a chimney breast, or in direct sun, relocate it to an interior wall away from heat sources.
• Allow to cool: If the room is genuinely very hot, allow it to cool naturally and see if E12 clears.
• Reboot thermostat: Remove and reinsert batteries after the device has cooled to room temperature.

If E12 appears even in a cool room, the internal temperature sensor may be faulty and reading excessively high. Replace the thermostat.