GE GSS25JEM Refrigerator Adaptive Defrost Board

I have a 3 year old GE Side by Side refrig GSS25JEMBCC. Seems to have
stopped going to defrost cycle (lots of snow forming in the freezer
around the ice maker output chute). Pulled the internal back freezer
panel and saw the coil coated with ice, and heater at bottom never
seemed to turn on.
I belive this runs with an adaptive defrost system, I could not find a
mechanical timer in the frig or the GE parts list. So I am guessing
there is a problem with either the adaptive defrost board, heater,
defrost thermostat, or some other thermostat.
Sound correct? Any debug tips? Is there a way to force a defrost on
this model (I see documents for other models on the internet but not
this one yet)?