There are a few things you would want to check. If you are sure that no equipment has changed, and no updates have been made to the equipment potentially modifying the firmware of your cable box, then there are a few simple tests. First, recheck your wiring connections, it is possible something came loose or is not making a good connection. Next, you will want to make sure that the IR-5000 is still getting good power as well and that the green LED is flickering while you are sending an IR signal. If you have a volt meter or multi-meter you can check the power supply. It should read 12VDC. You can also try moving the IR emitter to a different device. If you have a DVD player or stereo or something that uses a remote control you can see if it continues not to work with the new device. If it still does not work, you may consider trying a different emitter, if you have a spare, or if you are using a dual head emitter, try using the other head connected to the same cable. If you continue to experience issues contact technical support directly via phone at (714)424-6500, option 2.