What could cause a CAT 305CR excavator to suddenly lose all hydraulic power while the engine still runs fine?

[IamBruce_Driver]

I am trying to diagnose a CAT 305CR excavator that suddenly lost all hydraulic power while the engine still runs perfectly. The machine has around 7,500 hours and was only doing light blade work when the hydraulics completely stopped working. No burst hoses, no overheating, and no warning signs before it happened.