I have one of these - the TV can process signals from several sources - you need to tell it which source you want - on the remote control is a button - on my remote it's marked INPUT.
I use this button to tell the TV which signal to process - if you're unable to change the input selection then your TV is broken - it may be uneconomic to have it repaired - depends on how much a similar model will cost you.
Good Luck..., March 2017
