HDMI input on my 4k LG not working
LG flat screen 55uf645
Is not working it said check I puts
Yes tried all HDMI ports 4k only works on hdmi1
Try removing all HDMI cables and then "remove" the power cord for about 10 minutes (powering off is not sufficient ). Then Plug in the power cord, then one HDMI cable and try your device that way.
Also, something to note there is a known flaw with these tv's that cause a spike on the motherboard that cause the HDMI ports to stop working altogether.
Look under ratings and reviews.
Hopefully the reset will get you backup and running though.
The board replacement is not hard either though.
If after trying what Henry suggested to do, the HDMI inputs are still not working on your TV, then you need to replace your Main Digital Board.
If your Tv model code is 55UF6450-UA.AUSYLJR, then the part number for the main board you need to replace is EBT64048902
The solution sounds crazy but remove the main board and bake it in the oven to allow the weak solder joints to reflow, it will normally last about a year or two depending on use, when they go out again, repeat.