Ah, my 18" has the piezo-electric ignitor also. Yours doesn't even clack when your turn it? If it doesn't then it is faulty. Then you have two choices, replace it with a battery powered one, my choice, or contact Blackstone and have them replace it.
However still check the ignitor tip and make sure it is the correct distance from the flame tube.
However still check the ignitor tip and make sure it is the correct distance from the flame tube.