Your presenter may have lost contact with the USB receiver.
If you have a Voyager L4 unit:
1. Plug the wireless USB receiver into an available USB port
2. Press the Connect Key on the wireless USB receiver. The Status LED will start flashing. If the frequency search is not complete within one minute, the Status LED will stop flashing.
3. Remove the battery from the L4
4. Press and hold the Power/Mode button while reinstalling the battery. While installing the battery, the LCD screen will light up for one second then go out.
5. Release the Power/Mode button after the LCD screen goes out. The Status LED will go out at the same time.
6. The wireless transmission is reset and the L4 is ready to use.
If you have a Voyager L6 unit:
1. Plug the wireless USB receiver into an available USB port. Press the Connect key on the wireless USB receiver and the Status LED will start flashing.
2. Press the Frequency Search button on the controller.
3. The wireless transmission has reset when the Status LED stops flashing.
4. The L6 is ready to use.