lightning hit furnace, knocked out circuit board about 4 months ago. replaced w/ new. A/c unit working ,but when heat cycle is turned on, unit will cycle to let igniter glow , but will not let gas flow to ignite flame for heat. Any suggestions? thanks

Quite a few items can cause this problem especially if the unit was hit by lightning. I suggest calling a professional for ON SITE service. There could be more than one problem and as a safety precaution it should be professionally checked.