Your boiler is having trouble creating the spark or flame needed to start up because the internal ignition components are out of alignment.

Flow sensors check signal, pump or system

What causes this fault?

This fault occurs when the spark electrodes inside the boiler's burner move out of their precise position or become worn down over time. Without the correct spacing, the boiler cannot create a strong enough spark to ignite the fuel, or it may fail to detect that a flame has successfully started.