Your boiler has lost communication with your wall thermostat, meaning it cannot receive the signal to turn on your heating.

Check the ModuLine room thermostat. If the thermostat functions properly, the control panel is defective. Replace the control panel.

What causes this fault?

This fault occurs when the digital communication link between your wall controller and the boiler's internal computer is broken. The most common reason is a wiring failure at the connections or an internal electronic failure within the ModuLine thermostat itself, which prevents the boiler from receiving the command to fire up.