Diagnosis
The Heated Dry option is turned off, or you're using rinse aid incorrectly.
How to Fix It
Ensure the Heated Dry
If That Didn't Work
You might be interrupting the dry cycle by opening the door too soon. Wait at least 20-30 minutes after the cycle ends for the condensation drying to complete. Also, check that the high-limit thermostat (a service part) hasn't failed, preventing the heater from engaging for drying.
Heads Up
Plastic items and certain dish shapes will never get bone-dry without a heated dry cycle. It's a physics limitation, not a machine fault.