Diagnosis
This is a frost sensor trip. The evaporator coil is getting too cold, likely because the room temperature is low or the air filter is blocked.
How to Fix It
First, check and clean the air intake filter. Remove it, rinse with water, let it dry completely, and reinstall. Second, ensure the unit is in a room above 65°F. If the room is cold, the defrost cycle can't keep up. Move it to a warmer area.
If That Didn't Work
The frost sensor itself may be faulty or the evaporator coil is dirty. Unplug the unit. Remove the cabinet to access the coil (aluminum fins behind the filter). Use a soft brush to gently remove dust. Do not bend the fins.
Heads Up
Running the dehumidifier in a consistently cold basement (below 60°F) will cause this short-cycling. It damages the compressor over time. Use a low-temperature model for cold spaces.