Some 3pt's, when you pull the handle up, the lever stays in the raise position and the 3pt relief will be relieving. push the lever slightly down for neutral.
If you install a hyd pressure gage in the hyd system, you can see what the hyd is doing.
Hydraulic pressure in psi is different for different tractors. You need to know your pumps pressure capacity in order to adjust and trouble shoot the hyd system.
In an open center hyd system, fluid is always flowing, usually at no or little pressure. When you activate a valve, something is doing work, and pressure builds up until it matches the relief pressure and then it will relieve.
The relief valve on a FEL valve is close/adjacent to the IN port and most can be adjusted by turning a screw or adding shims.
The 3pt also has a relief valve.
Your lever position might be raise, neutral, and descend. In the neutral position, the fluid just flows through the valve doing no work.
You could make yourself up some hyd test sets/gages like these and monitor and trouble shoot the hyd system.