DIAGNOSIS The FryForce 360° system isn't circulating properly, or you're overloading the basket. Wet food piled up blocks the hot air from the bottom vent.
FIX Don't fill the basket more than halfway, especially with wet items like frozen fries or fresh veggies. Pat food dry with a paper towel first. Use the crisper plate—it lifts the food off the basket bottom. For really wet food, do a preheat for 3 minutes before adding it.
IF THAT DIDN'T WORK The heating element or fan might be underperforming. Test by cooking a single layer of something dry, like bread cubes, at 400°F. If they don't brown evenly and quickly, the heating system might be faulty.
HEADS UP Adding a light spritz of oil (use an oil mister, not aerosol cooking spray which contains lecithin that can damage the nonstick coat) makes a huge difference for crispiness. No oil often means no crunch.