If you want to check the pressure, either plug a hyd gage into the work ports QD's, or install a hyd gage in the IN port of the loader valve and you can check everything hyd .
The piston seals could be bad.
The valve could be bad.
The pump could be bad.
A relief valve could be open.
A flow and pressure check would be the best thing to do.
Pressure might be in the 2000 psi area with a good pump.