, are you perhaps letting the TV autoshut-off or get shut down with PC?
I just found using the 43UK6300PUE as monitor, if Quick Start+ is turned enabled, it will sometimes not wake properly then fail to accept HDMI input when it has shut down due to loss of signal or recieved shutdown command. It will see you move the cable from one input, you can change to that input, detecting and offering that input as a selection choice; however once selected it will say "No Signal". It lies.
Simply changing from Settings > All Settings > General > Quick Start+ from enabled to disabled and then turning the set off and on fixed the issue for me.
I am using a GTX 1070 to drive the display.
I am also a bit disappointed, somewhere in the TV's component, it is not 4:4:4 and does Chroma SubSampling
. It is silly that I can still confirm my old Insignia from Best Buy does 4:4:4 and yet some modern sets that should be far better do not. Sadly most of the test image links in the first few posts of that thread appear dead.
Otherwise it makes a good monitor. Size was perfect to view and read text at 3840x2160. Even works at 4096x2160.
I've mitigated the Chroma Subsampling issue to some extent by forcing stretching of a custom resolution (3456x1944 via NVIDIA control Panel) which helps (can still notice it a bit with some test images but most look good); also makes it a bit easier on my old eyes for reading.