Per your manual the column 4 wire begins at J207 pin four and is connected to all eight switches in that column of the switch matrix. Assuming your board is performing properly the signal travels from that pin on the board header- to the connector contact - then down the wire and through each one of the switches. If the signal is interrupted at any point none of the switches further down the chain will work.

So check your green-yellow wire for continuity starting at J207-4. Maybe you'll get lucky and it's pulled out right at the board.

DemoManSwitchMatrix (resized).png

Not necessarily. Check out this procedure at the Pinwiki to isolate the issue to either the MPU or the playfield wiring: https://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Switch_Matrix_Problems

If you determine the board needs repair (and you don't want to do it yourself) ChrisHibler and Borygard are both excellent choices. There are others on Pinside that do board repair as well, feel free to ask for recommendations.