Apple TV 4th gen ‘No Signal’

My 4th gen Apple TV was working well with my Vizio TV...until a couple of weeks ago. When I turned on the television and selected the HDMI with Apple TV I got a black screen with no audio, and a message box saying No Signal. The light on the Apple TV blinks when I use the remote, but nothing happens.

I have restarted my Apple TV, reset my Vizio TV to factory settings, changed both the HDMI cable and the HDMI port, and taken the Apple TV to the Genius Bar, where they told me ‘it worked fine when we plugged it in but we have restored the factory settings anyway’.

Bottom line, it still doesn’t work. Black screen, no audio, No Signal message and no amount of restarting or coaxing will bring forth a picture or sound.

Help.