|Try operating the TV with the "TV Listener" off. I would unplug it to be sure that the IR emitter on the TV is off. If the remote works with the Listener off, you may be washing out the emitted signal of your remote with the reflected signal from the Listener. Turn the Listener on and try moving the TV remote real close to the IR detector on your TV. If it works under these conditions, it would seem to confirm that there is interference from the Listener.
The infrared signal from remote controls is essentially light that your eyes can not detect. That is why you can often point the remote control at the ceiling or back wall and still control the TV. If the Listener emitter is very bright, it could effectively wash out the signal from the remote emitter. If this is the case, you might try moving the Listener emitter so that it radiates directly as much as possible to the headphones, and not to other parts of the room. If the TV is in an entertainment center you could put the Listener way in back and "block" emissions that would hit the ceiling and walls with potential to reflect back to your TV. If that does not work, you might get a universal remote. You would have to program this to control your TV. Sometimes the emitters on these have more powerful LED's. However, there is no guarantee that this will work.
If you can not get your TV remote to work under any conditions, here is some additional information that may be useful:
If your infrared remote has buttons for a VCR, cable box, or other devices; try pressing the TV button to be sure that you are sending commands to operate the TV and not another device.
If you have a camcorder or digital camera, you can test the output emitter on your remote. Point the remote at your camcorder and push various buttons. You should see flashing or continuous "light" from the remote. Camcorders and digital cameras have sensors that can detect the emissions from infrared remotes. If you do not have one of these cameras you can get an "infrared sensor card" from Radio Shack for about $6.00, part # 276-1099.
Infrared remote controls usually require codes to operate different devices, such as TV's VCR's Cable Tuners, etc. Here are some Zenith remote codes: 101, 142, 149, 177. Remotes may require re-entering the code when the batteries are removed, or a new code has been programmed in accidentally. There is usually a procedure for this on the back of the remote, inside the battery compartment, or with the manual.