And there's usually NOTHING you can do about that. I feel it was a shame that HDCP handshakes do this and some folk new to the area break down and flame in any discussion so it's rare to get down to why. Knowing why does not mean we can fix it. And you didn't ask how to fix it.
However there is that issue with HDMI interface chips and how we unplug all the HDMI cables then remove power from the HDTV for a few minutes. Power up the HDTV and connect HDMI and sometimes, sometimes that correct it.
The makers and more so the industry did a GM.
I have an LG 37LC2RR tv with an android box attached via HDMI. When I first switch on it works fine but after about 20 mins the screen goes black and then says no signal but the sound keeps going. I don't think it is the android box as if you switch the tv off whilst the signal is still there it is still working when the tv is switched back on up to two hours later. Any ideas as I am getting very frustrated with this.