Your boiler is not attempting to light the flame, which means you have no heating or hot water because the system has encountered an internal startup error.

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What causes this fault?

This fault occurs when the boiler's internal computer tries to start the ignition process but stops because it cannot detect a flame or verify that the gas is flowing correctly. The most common reason is an aging electronic component or a sensing probe that has become worn or dirty over time. Because the system cannot guarantee it is safe to stay lit, it prevents the burner from firing entirely to protect your home.