After double checking everything , You just reassured my suspicions
The customer wants a second opinion from an other company, he's entitled to that.
Thx again

so from what you are describing, when you add an external power source to the solenoids the functions return to working.

on this system on this yale truck that 'fluid power system board' as you put it is called a MIB, this is other wise known as a Main Interface Board.
This controls the functions and also is programmable to control how the functions work and unfortunatly is also what supplies the power to the solenoid coils when a function is selected to make them operate.
find the connector from the harness going to the mast control cable and check the voltage outputs at the connector, it may be labeled a PWM cable.
If you find the outputs are the same voltage as you are seeing at the coils on the other end then this is most likely your problem.
From what it sounds like the MIB has a bad output voltage or could be programmed incorrectly.

Tried swappping solenoids and valves from side to side, also checked for contaminates/ no change
I disconnected the three wire harness from the mast and manually powered it up with a portable 24volt power supply, to my surprise the aux works
I don't see a DC to DC inverter on this machine, I see the main controller and a fluid power system board with a digital read out that changes depending on function selected.
Any thoughts :-/

Had a similar issue with a NDR030. Traced it to the solenoids in the manifold that's mounted on the carriage on the side closer to the operator. System was contaminated and particles kept getting stick on the hydraulic side of the solenoid. After changing solenoid two times I finally opened the hoses and sprayed out half the tank through the open houses to flush the system and it's been good ever since.

Thx for the info swoop, I still have a few questions...
The cable through The mast to the coils checked out.
The cable has only three wires, one constant power and two activation wires to ground. I have only 6volts at the coils on sideshift and on reach ( I assume since there is not a 4th wire for the tilt then the coils must be in a neutral position for the tilt to work )no power to the pentograph for tilt when selected but this is the only function that works even with the control cable in the mast disconnected.
The coils indicate they are 24v, why would I only have 6v?

first thing i would check is the control cable going through the mast, check the wiring at the control valve on the pentograph and running through the pentograph.
most likely cause is a bad coil or damaged wire or disconnected solenoid coil.