Diagnosis
The ionic generator or its indicator LED has failed. The dryer's heating and fan functions are on a separate circuit, so they still operate.
How to Fix It
Unplug the dryer. Remove the nozzle and front grille to access the ionization chamber near the air outlet. Check the small, needle-like electrodes for heavy lint buildup or breakage. Clean them carefully with a dry brush. Reassemble and test.
If That Didn't Work
The high-voltage generator board for the ions is likely faulty. This is a soldered component on the main PCB. Visual inspection may show a burnt resistor near the transformer. This requires board-level repair or PCB replacement.
Heads Up
The ionic feature requires clean, dry electrodes. Using the dryer in a very humid bathroom can cause corrosion and short the circuit.