Ground control works fine to start engine, cannot start from platform. All other controls at the platform works. Tested switch and it is ok, I can't seem to trace where the wire goes from there. Wire is white/yellow marked 48-1 as well as the wire from the ground switch.
Welcome to HEF reverrock. :drinkup Ground controls: wht/yel 48-1 leaves start switch and goes to terminal #1 in lower control box, wht/yel 48-1 leaves terminal #1 and goes to starter relay. You've confirmed this circuit works. Platform controls: With ignition on (E stop pulled out, foot switch not depressed), make sure you have voltage on yel/red 2-9 going to start switch. If no power, you have problem with either foot switch or cables. If power present at start switch, wht/yel 48-1 leaves start switch and goes to terminal #1 at platform box. Black wire from boom cable connects to terminal 1, carries start power down boom and connects to terminal #1 in lower control box, the circuit you've confirmed works. If you have power from upper start switch sending power to terminal 1, but no power getting to terminal 1 at lower controls, you have a boom cable problem.
Are there any spare wires that I can use from the platform to the control box.
That's hard for me to say as I don't know how your machine is configured and what options it was fitted with, but it's possible there are spare wires. You should be able to pop open the upper control box and tell. Every JLG that I've worked on, if there were spare boom cable wires, JLG left a portion of the wire sticking out and not nipped off where the cable jacket is stripped back.