In a situation where a unit that has been functioning correctly has suddenly stopped for no apparent reason the issue is likely an internal electronics glitch caused by a power surge. To resolve this issue an internal electronics reset is required.
Disconnect the transmitter (base station) from both the audio source and the power source and at the same time remove the batteries from the headset. Leave the system disconnected from power and the batteries out of the headset for 15 minutes. This gives the internal electronics unit a chance to reset back to factory settings.
NOTE: If the batteries need changing it is best to use AAA size 600-900 miliamp NiMH batteries.
After the reset period reconnect the system to power and put the batteries back in the headset. The aim when connecting the audio cables is to get a GREEN light on the transmitter because it indicates that an audio source has been located by the transmitter. Once you have the GREEN light on the transmitter then it is simply a matter of using the TUNE dial on the headphones to tune the headphones into the transmitter.
If the GREEN light doesn't come on or comes on and then goes away when the transmitter is plugged into both a power source and an audio source then it means that the audio signal is is too low (or not getting to the transmitter at all). The transmitter needs a nice, strong signal to work with and if the audio signal is very weak (or non-existent) the internal electronics will shut off within 5 minutes to conserve battery life. If this is the case then the signal level needs to be increased before reaching the transmitter. This can be accomplished by turning up your source on variable-level outputs (TV Volume) or by increasing the signal from a fixed-level output (increasing the output level to the audio output jacks which is done through the TV set up options). Try increasing it in small increments to prevent overload which results in distortion. Also check to see that you are connected to outputs and not inputs.
If there is no way to increase the audio signal and hence the GREEN light does not come on and stay on on the transmitter it would be recommended to try to connect to a set top box (cable box, DVR, HD receiver, etc) through its audio outputs or connect through a headphone plug in order to get a stronger signal.