My maytag skybox does not cool very well

1) your box may be low on freon,
2) fault thermostat may cause unit run non stop,
causing evaporator to ice up and blocking air
circulation,
3) Dirt condensor thus reducing operation efficiency.

Check the simplest problem first - make sure condensor
coil is clean. if not, use a vacuum cleaner to clean condensor.

For # 2 is more likely if the evaporator has a fan.
If it has, check to see if it runs; it is behind the back panel inside box.
While at that, see if evaporator coil iced up. If it is defrost using hot water and turn it on setting thermostat to normal temp. setting.
If it work fine and later develops same problem, replace thermostat.

If the above 2 solutions don't solve the problem, call a technician to check freon.