DIAGNOSIS This indicates a refrigeration system failure. The compressor may not be engaging, or the unit has lost refrigerant.
FIX First, verify environmental conditions. The room must be above 65°F (18°C) and have relative humidity above 45% for the unit to activate moisture removal. If conditions are correct and the coils do not get cold, the system has failed.
IF THAT DIDN'T WORK Listen for the compressor attempting to start. A rapid clicking or humming that stops points to a compressor start component issue. This requires professional repair.
HEADS UP A common misdiagnosis is not waiting long enough. In a moderately dry room (below 50% RH), the unit may run the fan but not activate the compressor, which is normal.