Hello, my name is***** be happy to assist you.
Please allow me to ask you a few questions to diagnose the problem.
- Do you have another video device such as DVD/Bluray player to hook into HDMI
input of TV as a test to see if TV shows picture or HDMI input still stays grayed out?
If TV shows picture with sound that means TV itself is fine and connected Cable Box and Apple TV device are defective.
If TV still doesn't show picture of DVD/Bluray then HDMI processor chip on main board of TV isn't working and entire main board of TV will need to be replaced. If I could have your TV model number then I can provide you approx repair cost info that will help you to make decision about this TV repair or invest that money on new replacement TV.
I would also suggest to unplug TV, cable box and Apple TV device power cords from wall outlet for 10 minutes to reset, replug back in and check if it helps to resolve the problem.
I trust my input will help you out. Please feel free to respond if you have any additional questions.
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