No sound coming through my Sennheiser wireless headphones

Turning the transmitter on and off (Fig. 5)
Turn on the sound source. This automatically activates the
transmitter and the green LED “ON/OFF” lights up. If the sound
source is turned off, the transmitter is automatically deactivated
after approx. 3 minutes (the LED “ON/OFF” goes off).
Note: The automatic level control only functions if the volume of the
sound source is sufficient.

Try checking the power connections, on the left hand side, that takes the 2.8 volts over to the right hand side. It would appear that these had shorted out on my headphones and stopped the reciever from working. I moved the wires apart and the headphones started working. I hope this helps.