Possibilities:

• First, check if the transmitter battery is drained or polarity inserted incorrectly. Change accordingly.
• The frequency between the microphone and the receiver does not match.
• Receiver has PILOTONE function while handheld microphone does not.
• Malfunction of the receiver audio frequency circuit.
• Malfunction of the microphone capsule.
• Receiver is not power-on or plug-in.
• RF signal does not illuminates after the microphone is power-on indicates the radio frequency circuit of either microphone or the receiver has a problem. If RF signal illuminates after microphone power-on but has no audio sound, this indicates problem with audio frequency circuit of either the receiver or the microphone.