Ensure the knob is set on the pilot setting (small spark picture) and is fully depressed or held down long enough to purge air from the line. If the pilot flame is not touching thermocouple, clean pilot tube using q-tip with alcohol. Run 2 inches to bottom of pilot tube & twist around. Blow out with straw or 30 psi or less. If the thermocouple connection is loose at control valve. Then hand tighten until snug, then 1/4 turn with wrench.