Hydraulics won't lift on TO-30

Maybe you'll be lucky and find that your relief valve opened and didn't close all the way because some dirt got in it. Open the right side access panel and with the engine running and the pto engaged so that the pump is driven, look up at the lift cylinder and see if there is more than a few drops of fluid coming down from it. If there's a lot of leakage the cylinder could be damaged. (DO NOT, UNDER ANY CIRCUNSTANCES, STICK YOUR HANDS INTO THE HYDRAULIC COMPARTMENT WHEN THE ENGINE IS RUNNING!) Look down where the pump is at and see if the there a lot of turbulence near the back of the pump and some noise. that's the relief valve and if it's noisey and turbulent it's either damaged or has dirt in it holding it open. You'll have to clean it or replace it if it is damaged.Look at the linkage and see if it's damaged. Move the lever full range up and down and verify the linkage is moving.

Shut down the engine and feel down where the control fork connects to the control valve. The fork is attached to the T shaped rod that shuttles the control valve. If it's not connected then the control valve won't respond to lever inputs. Spread the control forks and slip them back on the control valve.
That's all I can think of without more info from you.