Your boiler's main control panel is failing to communicate with the internal electronic board, meaning the system cannot receive commands to heat your home or water.

No reception by the local user interface As F.11

What causes this fault?

This fault occurs when the internal pressure sensor detects a sudden drop or spike caused by a lack of water movement. It is usually triggered by a physical blockage in one of the heat exchangers or a failing pump that can no longer push water through the narrow internal pipework. This effectively chokes the system, causing the boiler to shut down to prevent overheating.