Quoted from cottonm4:Try swapping them with the bulbs next door and see if they work. As noted below, those empty sockets are for flasher bulbs. You would have to contact Comet Pinball to verify if what you are holding is a flasher. It looks like a flasher bulb but I am not positive.
https://www.cometpinball.com/collections/flashers
1) Yes they are flasher bulbs.
2) Question is, is that the correct socket they are in. The flasher take a different one than the normal lamps and won't fit PCB.