Your boiler is failing to ignite the burner at the required power, meaning it cannot provide heating or hot water.

Burner does not instantly operate at or near maximum gas pressure / 230V at pin 1 of terminal X4 (Brown wire)

What causes this fault?

This fault occurs when the boiler's control system attempts to fire the burner at full power but fails to detect the necessary electrical signal or gas pressure. It is typically caused by a failing gas valve that cannot open fully or a fault within the internal control box that prevents power from reaching the ignition components. In some cases, a loose or damaged wiring connection between these two parts is the root cause.