Your boiler has lost its connection to your room thermostat or heating controller, so it may not respond to your heating settings, though this is usually a wiring or communication problem that can often be fixed.

DIY fix possible

Turn your heating controller or room thermostat off, then back on, and wait a few minutes for it to reconnect to the boiler.Check and replace the batteries in your room thermostat or controller if it runs on them, and check it is set to the correct mode.Look at the wiring at the thermostat end only (not inside the boiler) to confirm the wires are firmly connected and not damaged, then power the boiler back on and see if the code clears.