An air conditioner's cooling mechanism is governed by its internal compressor. If the compressor is off, then the cooling mechanism or element fails function.
This happens because the temperature setting on the air conditioner and the room temperature are the same or because the "Fan-Only" cycle has been activated. If the compressor fails to turn back on after you've adjusted the temperature or activated the cooling cycle, then the compressor might be broken and require service.
If the fan is running, but no cool air emits from the air conditioner, activate the internal compressor by lowering the temperature setting. If cool air was blowing from the louvers, then stopped, the air conditioner regulated the temperature of the room to the desired thermostat setting.
Press the down directional button on the front of the AC unit or on the remote control to drop the thermostat down. This will activate the compressor and cause the AC to blow cool air.
Keep lowering the setting, until you hear the internal compressor kick in. You will feel cold air come from the louvers shortly after the compressor turns on.
If the "Fan-Only" button has been pressed or if only the fan portion of the air conditioner is active, then the compressor will not kick in, until the cooling mechanism is also activated. The fan is separate from the cooling element of the air conditioner.
It acts to circulate the air that comes through the air conditioner's front grille out of the unit. To activate the cooling mechanism of the air conditioner, press the "Cool" mode button repeatedly, until you reach the desired cooling level.
Confirm that the thermostat is set lower than room temperature.
Sometimes outdoor conditions cause the coils inside of the AC to freeze. If the coils are frozen, while the unit is in cool mode, then cool air, ironically, fails to blow from the unit.
Raise the temperature and fan speed using the controls on the front panel of the unit or on the remote control to thaw the coils. Once the coils are thaw, slowly lower the temperature, until the desired cooling level is reached.