Is the unit plugged in or is the plug loose?
Is the fuse blown or the circuit breaker tripped?
Did you restart the unit within 3 minutes after a power failure? If the power was off for less than 3 minutes, and you restarted the air conditioner within 3 minutes, a protective device may cause the compressor to shut off, preventing cooling for about 5 minutes.
Is the MODE set to fan only Mode?
Cooling will not take place in the fan only mode. Change the MODE setting 
Is the filter clogged with dust?
A dirty filter can cause the cooling coils to freeze. If this happens, clean the filter and replace. Run the air conditioner on the MED FAN setting until all ice dissipates.
Is the temperature set properly?
If your room is too warm, adjust the temperature setting lower. 
Is the window exposed to direct sunlight?
Close curtains or blinds to minimize solar energy heating the room. 
Are the windows or doors open?
Close all windows and doors for maximum cooling.