Why has my refillable flexible neck butane lighter ceased to ignite?

A year or so ago I purchased a long necked refillable butane lighter along with a canister of fuel to refill it with. It has suddenly stopped lighting. When I look down into the business end I see a spark occur when I pull the trigger but it does not ignite. When I pull the trigger holding the business end over a candle flame it lights. But it won't light on its own when I pull the trigger. Yes, I am holding down the safety lock.