Not sure there! You do have 12v to the panel somewhere or the red light would not show. On our 1991, I had a busted "momentary"? whatever the word is --rocker switch, so the panel seemed to be broken, but you can buy the switch so that fixed that.
First I would pull the panel out and get at the back where the slider and the push buttons' wires are and see if there is 12v across them individually and clean up contacts as required, buy new parts if available. If no joy, perhaps you can "upgrade" to a 1990s panel that is less complicated. Maybe somebody "parting out" an older RV.
