Several faults could result in an inoperative compressor clutch. Assuming intact wiring and fuses, the mostly likely cause is an inadequate refrigerant charge: the clutch (and thus compressor) is rendered inoperative if system refrigerant pressure falls below a set level. The Nippondenso compressor used with this vehicle has no oil sump and depends on the refrigerant to carry its oil.
If gauges are unavailable, a quick check for adequate freon charge can be accomplished by momentarily depressing the Schrader valve located on the return (low pressure) line. If minimal or no pressure is present, then the system likely has an inadequate freon charge (as well as a leak) and is thus inactivated by the freon pressure switch.
If the system is charged, locate the freon pressure switch (two pronged switch adjacent to the inflow side of the receiver/drier), disconnect and jump the two leads; turn the ignition on and activate the A/C (no need to start the engine). If the compressor clutch is heard or seen to engage, then the freon pressure switch is likely defective.
BTW, has the evaporator ever been replaced?