Diagnosis
The heating element is likely failing, or the high-limit thermostat is cutting it off prematurely. No heat means no evaporation during the dry phase.
How to Fix It
Run a cycle and listen carefully during the dry phase. You should hear a faint hum from the heating element under the tub. After the cycle, unplug the dishwasher and remove the lower access panel. Use a multimeter to test the heating element for continuity. It should read 10-30 ohms.
If That Didn't Work
Test the high-limit thermostat. It's a small disc attached to the tub near the heater. It should show continuity when cool and open when hot. If it's open when cool, replace it (part number W10101069).
Heads Up
Plastic items and some dishware types will not dry without heat. Use the heated dry option. Ensure you are using rinse aid, as it reduces water surface tension for better sheeting action.