Activation switch on system 9 is not in the switch matrix.
my copy of the manual is hard to read but it looks like the input is J18, and the outputs are j19. So if you disconnect both of these, you can check all the outputs to see if any are shorted to ground - if they are, the problem is on the board. If you have a logic probe you can follow the signal from the inputs at j18 to the output at j19, if any output doesn't change as you alternately ground its input pin, then let it float, the component is bad.
If nothing is grounded at the output without connectors on, put the input connector back on. Test the outputs again. If you now have an output shorted to ground, the problem is on the playfield, something is grounding out the special solenoid activation switch permanently. There should be a resistor and capacitor on one of the solenoid switches that poke through the playfield, you can temporarily cut one side of the cap lead, test again.