Refrigerator Gas/Elect switch

Hello All,
Slowly getting things together, but had a question.

Have the standard Dometic 2way refer in my TT. The switch to change input is set to Electric.

I cannot get it to turn to Gas. It just stops at Elect.

Does this have a safety interlock that the unit has to be powered or hooked up to Propane for it to turn to gas position ?

Thanks for your thoughts. Ketch