Without going in depth into why this happens, suffice it to say it just does. Now it may even be that the old cable actually worked perfectly for ten minutes, an hour, or even a day, then suddenly it stopped working, and you think waahh it was working fine its not the cable, but in fact it is.
For example! You may have had a HDMI 1.4 (or lower) cable which worked perfectly with your older HD 1080 TV but you’ve now got a UHD TV which requires an HDMI 2.0 compatible cable (higher bandwidth for the most part) but you’ve not changed the cable. In my experience this is most often cable related. The handshake happens so that a connection between the source and your TV can be established, and a channel for the communication of you signal can form… ie you can see the picture from your film player, service provider or picture source. There are a number of issues that can cause this problem, but essentially it happens when the HDMI handshake fails. Oh, and I then chatted with another samsung person and she said the guy I had previously chatted with needed additional training and she would tell her manager about him. But why the Samsung tech support person didn't give me this info is what I couldn't understand and then I get the solution from a guy my age (61) at a Best Buy! Anyway, thought some of you might be interested in this info and update. We figured out that the front of the tv at the bottom right there has nothing written there, just the sleek black frame around the flat screen, but we began pushing on the front in different places and, voila, the "source" choices showed up on the tv screen and then we had cable back again!! Going to return the remote we just bought and never opened.
Store guy said I had to get the programmable remote but then he showed me the buttons on the back of the samsung tv's in their store that work also as a "source" button! I had never seen a power button or any other button on the back or along the bottom of our tv, so I bought the $76 remote and on the way home, my spouse says "lets look at the user manual again to see if there are buttons somewhere we couldn't see. So I called Best Buy the next morning (Saturday) to see if they had it they only told me they have "universal" remotes. After live chatting with a samsung tech support guy for half hour late Friday night, and he saying I needed a samsung remote (which I had lost in a move two yrs ago), so I could use the "SOURCE" button to go between cable and HDMI, etc. Well, I finally had success the next day, getting back to being able to view our regular cable programming channels.