Getting the system to light the pilot, the white knob would have no effect.
You should push in on the red knob when turned to pilot, light the pilot and keep holding the button in for maybe thirty seconds. When you release it the flame (pilot) should stay lit.
I would start by giving the unit a good cleaning.
The thermal couple could be weak or the flame not good enough to heat it up. You could hold a long lighter under the thermal couple to generate more heat to see if pilot stays lit.
Does the other appliances work properly? It could be the small pilot flame is due to a LP regulator failing or out of adjustment. Depending on how old it is you may want to get a replacement.
