Gas Burner Assembly Cowling.
The gas burner assembly has a protective cowling which has two screws securing it, indicated by the yellow arrows. The screw under the the water container is located on the back wall of the fridge. Having removed the screws the cowling must be squeezed in the direction of the red arrows, then pulled out.
As the flame was difficult to see from inside the fridge I fitted a mirror on the inside of the cowling to reflect the flame to the viewing interior pipe. If this is not convenient to others, try and polish the inside surface to a high sheen to enable an improved reflection for the viewing tube inside the fridge.