If you don't have enough charge in the system, the LPCS keeps the compessor coil from energizing.
Check for power into the LPCS but not leaving it. If you have power leaving it, check the WOT relay wiring (in the CCRM). Power normally flows through the common and Normally Closed terminals except when one achieves WOT, in which case the EEC sends a ground pulse to energize the coil and open the circuit to the compressor clutch.