Any battery damage ?

Scroll through the adjustments a few times. Hold the button down ) Then when it goes to attract mode, see if it works then.

LTG : )

Sounds like classic trough switch issue - game will never start unless it “sees” all three balls.

And yes acid damage can cause this too.

I would
Carefully inspect battery holder area for green stuff, and do a trough switch test/visually inspect all switches and check for loose
Wires
Or
Diodes.

Don't go fooling around with your wires and connectors first thing. Follow LTG & CrazyLevi 's advice, move on from there if needed.

Pull and check it's fuse with a meter.

LTG : )

In the back box on a board. A manual can help you. https://www.ipdb.org/files/1176/Williams_1986_High_Speed_Instruction_Manual.pdf

LTG : )

Not easy to find in the manual. Power wiring diagram on page 47 and Interboard Signals diagrams on page 50 (upper right board) have them listed.

Much easier to use the tech chart over at pinballrebel.com - http://www.pinballrebel.com/pinball/cards/Tech_Charts/Williams_High_Speed_Tech_Chart.pdf

Pinball Life, for all your fusing needs: https://www.pinballlife.com/search.html?Search=fuse

Are there three balls in your game or two? You should have three in there.

Don’t be surprised if the fuse blows, which means you have a short or a cooked coil somewhere. May as well look around under the playfield for a coil that looks burned or melted or fused up somehow.

Fuses sometimes “just” blow but there’s often a reason that has to be addressed.