It has been a while since raymond used that drive system and those trucks have been long gone from our warehouse. I do not have any manuals left from that era but going by the previous code description pc contactor detected open when commanded closed this is what i have to offer.
Side cover removed you will see two big copper contactors, one is the pc contactor and one is the lift contactor, you can trace the cables coming off them. The lift motor would be sitting horizontal, the pc would have cables coming off it going to the aux motor and it would sit vertical. When you turn the key on, the pc/aux contactor should pull in for a second and then you would hear the aux motor run and cycle and then shut off. Judging by your previous comment you do not hear the click when turning the key on, this is most likely not happening.
So you can disconnect that battery and manually push the contactor in to make sure there is no mechanical issues, then you can check the resistance of the coil on the backside with the two push on wires disconnected, i think it should be around 50ohms but compare it to the lift contactor and they both should be close. You can also hook the two push on control wires back on and back probe each of them and then turn the key on and see if you are getting voltage for a second or two as they truck turns on. This should be battery voltage ie around 24v
Most likely if it is getting no voltage to the contactor then on the very top the most upper control card, it is called the system card, the vfc card screws vertically onto it, and there are a few horizontal cards that push into it, one of them is the cd8 card, if you are getting no voltage at the contactor most likely it is the cd8 (coil driver) card or system board, but there is no real test for these.
CD8 card would be the cheapest and easiest to try, if you change the system card or buy a used one make sure you change all the chips over from you old card and put the old vfc onto it as there is software chips in them that needs to match, but it has been so long that i don't know where exactly they all are.