Aircon Not cold enough
Clogged Filter
Fundamental Concept:
The aircon is producing cold air, but it is not strong enough to reach you. Solution is to improve on the air flow.

Systematic Troubleshooting (for layman):
Step 1:
Open the aircon lid cover, you wil see 2 pieces(usually) of plastic net filters.

Step 2:
Check if the filters are dirty.

Yes, they are as dirty as the picture above.
No, they are okay.