Flow = speed, pressure = power. If you don't have the power to lift the front end, you don't have the pressure. If the pump pressure is good, then it's bypassing somewhere. Most likely the cylinder seals or the control valve. Cold oil is thicker than warm oil, so any sealing problems are going to get worse once it's had a few cycles.
Hydraulics are simple to troubleshoot, just messy. Personally, I'd disconnect the lower hoses from the cylinders, let the oil drain out, then try to curl down. If you start getting an increasing amount of oil coming out of the cylinders, the seals are bad. If not and it still won't curl down, pressure isn't making it to the cylinders. At that point I'd be looking at the valve bypassing internally, hoses collapsing internally or bad quick connects. If it does curl down with the bottom hose disconnected, you probably have a return line blockage, so again, valve, hoses, quick connects.
Hydraulics are simple to troubleshoot, just messy. Personally, I'd disconnect the lower hoses from the cylinders, let the oil drain out, then try to curl down. If you start getting an increasing amount of oil coming out of the cylinders, the seals are bad. If not and it still won't curl down, pressure isn't making it to the cylinders. At that point I'd be looking at the valve bypassing internally, hoses collapsing internally or bad quick connects. If it does curl down with the bottom hose disconnected, you probably have a return line blockage, so again, valve, hoses, quick connects.