The main reasons for air conditioners not cooling are:

1. The room has high humidity with minimal temperature difference between indoor and outdoor.

2. Outdoor condenser surface is dirty.

3. The refrigeration system has air in it.

4. Insufficient Freon (commonly referred to as not enough snow type)

5. The air conditioner's power is insufficient, leading to insufficient cooling.

6. Extended periods without cleaning the filter result in reduced airflow.

7. Due to improper installation, the copper piping between the outdoor and indoor units of the air conditioner is excessively long. It is recommended to shorten the length of the copper piping between the outdoor and indoor units of the air conditioner.

8. Voltage often fails to reach normal levels, with insufficient supply voltage and unstable voltage supply, especially during peak electricity usage hours when this issue tends to occur more frequently.