If your hyd system is an open center hyd system, and all valves are connected in series correctly, then with all valves in neutral, the pump is just pumping fluid through all valves and to tank.
Typically the hyd fluid would flow from the pump to the FEL valve and then to 3pt and then to tank.
Install a hyd pressure gage at the IN port of the FEL valve and take some readings.
A flow and pressure test would be good.
So if fluid is flowing through the FEL valve, and out the PB port, then the 3pt should work, and you can verify if pressure is being developed. The OUT port should go to tank/return hose.
It sounds like the FEL OUT port and the PB port is not connected correctly.
Can you show some pictures of the PB side of the valve and where the hoses go to?