Relay reports that no thermostat is detected; app shows the Relay online but no temperature or control from the thermostat.

Safety: You can perform all steps without touching mains wiring. If you later open the boiler or Relay wiring, switch off power first.

• Replace batteries: Open the thermostat battery compartment and install fresh, high‑quality alkaline AA batteries, observing polarity. Avoid rechargeable NiMH cells.
• Check thermostat display: Ensure the thermostat screen turns on and responds to button presses. If the screen is blank after new batteries, the thermostat may be defective.
• Reduce distance and obstacles: Move the thermostat closer to the Relay. Avoid placing it on metal surfaces or near large appliances that can block RF signals.
• Re‑pair thermostat: In the Netatmo Energy app, go to Settings > Manage my home > Thermostat > Pair with Relay and follow the instructions to re‑associate the thermostat with the Relay.
• Check for RF interference: Temporarily switch off nearby RF devices (wireless alarm sensors, baby monitors, etc.) to see if the link stabilizes.

If the thermostat never appears in the app despite good batteries and close proximity, either the thermostat RF module or the Relay RF module may have failed and the affected unit should be replaced.