We do custom installation, Whole-House-Audio, and System Integration.
Reset your unit. This is simple to do. Just unplug your unit for a couple of minutes. Then plug it back in. Then, retry the previous function or operation of the unit. Many times, that's all someone needs to do.
Try another source. For example, a DVD player or video game. If it works ok, then, the problem may be the cable box.
If you have a surge protector ( and you should have a surge protector) check the switch.
Plug a lamp or something into the outlet, make sure that outlet has power.
If you still need service, look for any blinking lights on on unit. Count the number of
blinks. This may be the unit's error code.
If possible, know the brand of your unit and get the model number.