Hi,
You will have to excuse me as it is 15+ years since working on these wonderful machines. The fact that you have not got all the electrical circuitry connected could be a problem, but .... i think that I have spotted something. You say that all the hyd systems work by using hand controls direct to spool valves, but not electrically. Now I am wondering if one of the emergency taps has been shut. These are there in case of an electrical failure and will allow systems to be operated in an emergency, but without any safety features, ie load cut outs, etc.
If you go to the platform behind the cab, looking rearwards, you have a bank of spool valves, (magnet valve block), to the left is a square block with a square tap in it, on the end is a line stamped, showing postion of the tap, normal use it is a through flow (lined up with pipe unions), emergency postion is to shut that flow off. Check this out and if it is shut, turn it to open and try your electrical solenoids again.
regards, Richard