Without the plasma cutter even attached to the electronics box at all could you put a multimeter on the torch on off port on the back of your electronics enclosure set to the ohm setting. Then do a manual fire in fire control and see if it starts reading resistance (closed) or better yet you could do the same test at CPC cable remove from your plasma torch.
Connection three and four.
*And obviously all electrical stuff’s at your own risk.
We are just trying to determine if a signal is making its way at least to the CPC Port of your plasma cutter.