Your fridge does NOT have a thermocouple......
The 'spark electrode' provides the spark for ignition AND is used as the means of 'proving' flame lit off.
Spark electrode needs to be positioned directly centered over burner slots so main flame engulfs electrode.
Lighting off when sparking and then going out when sparking stops means no proof signal is getting back to circuit board:
Reposition electrode
Clean electrode
Clean electrode connections (at electrode and at circuit board)
Electrode shorted/grounding
Electrode NOT properly grounded