Hi, Try a new cable. My wife purchased a Dell Inspiron a month ago and couldn't get it to display on our fairly new 4K smart TV. The laptop recognised the TV name and defaulted to duplicate screen as soon as it was connected but the TV remained blank. Dell spent hours with remote access etc but couldn't find a fix. The HDMI cable we were using works perfectly with my older HP probook and appears expensive with LED lights at each end and a heavy blue cable. I found a very plain little black HDMI cable lying around and on a hunch tried that and it worked!! Also works on the older laptop. No idea why - does anyone have an answer?
Faced the same problem, but but a solution by trying multiple tims
1)If HDMI cable is connected, remove the cable.
2)Switch off the TV, remove the TV power cable and keep pressing the power button for a few seconds.
(This gets rids of all the stray capacitances in the circuit. If you don't know what I'm talking about nevermind. Just do it or go through some theory of Electronics engineering.)
3)Now connect the HDMI cable.
4)And finally connect the power cable and switch on the TV.