Doc here,
Check the ground (Post switch wires) Between the switch/Lamp and the Door posts, this is usually where the problem lies when BOTH or ALL Dome switches don't function..
The switches , You will Note, are a single wire Switch..They pick up body ground from the switch body, and through the center conductor, implies ground on the Dome light system, The lamp is wired "Hot at all Times" and the ground is the wire that goes to the switches to complete the circuit.
Doc.