Always check the thermostat and adjust it as necessary. It may seem obvious, but switching the thermostat from "Automatic" to "Fan" can sometimes explain why an air conditioner is running but not cooling.
When the switch is in the "Automatic" position, the thermostat activates the air conditioning when the interior temperature exceeds the desired preset temperature. The device will blow air through the duct system if the switch was unintentionally set to "Fan," but no cooling will occur.
Change the dirty filter if needed.  Your AC system's return-air filters may be clogged, dirty, and impair air flow if it has been more than a few months since you last changed them. The AC system can only draw in a meager amount of air when filters are clogged with animal fur and dust, and as a result, the airflow is weak.