I'm working on a 1985 Williams Comet.

It needed a flipper power board and a sound and speech board, numerous lights and flashers and had the original rubber on it that has now turned to dust and a clay like substance.

I have everything sorted out and have repaired the cracks and holes in the ramps with Plastix (amazing stuff actually).
All thats left is the backbox lights are not working but after replacing all the flasher bulbs the flashers are working great.

The Playfield GI is perfect and working solidly.
All of the displays are clear and bright.

So Is it a wire off or broken in the backbox? All the fuses are new and perfect, tested many times with a meter.

What would be the first things to check as far as power to the lights in the backbox only?

Ill look for it. A picture of it would really help in case its missing on this game.

Any other Ideas?

I resolved it by smacking the relay on the floor a couple times. Evidently it was just corroded and jammed up a bit, not being used for 20 years.
I did find a few good replacements online from $4.80 to $20.
Marcospec also has replacements.
Its just a 5 lug 24v automotive style relay, I think normally open.

Thank you so much for everyone who responded, I wouldnt have even known that the relay existed without pinside!