DIAGNOSIS: You're probably overcrowding the basket. Air fryers need space for the hot air to circulate. If the basket is packed, you're just steaming the food.
FIX: Cook in smaller batches. Don't stack food or fill the basket more than halfway. Also, a lot of folks miss the preheat step. For the air fry function, you should always let it run empty for 3-5 minutes until it beeps, then add your food. Finally, give the basket a good shake halfway through the cook time. That exposes all sides to the heat.
IF THAT DIDN'T WORK: Check that you're using the right accessory. The air fry basket should be used, not the solid pot. Also, pat your food absolutely dry before cooking—excess moisture is the enemy of crisp.
HEADS UP: The air fry function runs the fan constantly. It's louder than the other settings, that's normal. If the fan isn't running audibly, then you have a different problem.