There are numerous reasons that could cause your air condition not to cool in your flats or villas.
If the AC blow warm / hot air some times and blow cool on other / some times. Then the Air condition fan may be configured as ON instead off AUTO. So set the thermostat to AUTO to get cool blow air on all times.
A dirty / dusted AIR filter reduces airflow in the AC. The filter dust will be causing some more problems.
Try to clean the air filter on twice in a month or once in a week to get good AIR blows.
For some reason the condenser cannot dissipate in case of dirty. In those cases the air conditioner struggle to cool your rooms or flats. The air conditions inside unit absorbs heat from your air and transfers that heat to the outside units.