Your boiler is unable to create the electric spark needed to light the gas burner, meaning your heating and hot water will not work.

Spark Generator Fault: Check wiring, if OK replace spark generator

What causes this fault?

This fault occurs when the boiler's internal electronic starter fails to send a high-voltage charge to the ignition probes. The root cause is usually a breakdown in the spark generator’s internal circuitry or a loose connection that prevents the electrical arc from jumping across the burners to light the gas. In some cases, the control board may be failing to send the initial command signal to begin the ignition process.