I am trying to connect a windows 10 PC to my tv. The TV will display the boot screen but once the login screen comes up, the tv goes black and stays black. This pc works via HDMI on other tvs and monitors I have tried. I have tried all the HDMI inputs and tried changing between auto and HDMI2.0 on each. The firmware on the TV is up to date as is the PC OS.
Sounds like your computer isn't using a resolution that your TV supports. Remember that it's not only the resolution itself, but the refresh rate has to be correct as well. Your TV supports 4K, but perhaps your computer doesn't, so it's sending a resolution/refresh rate that the TV doesn't like. HDMI is supposed to auto-negotiate the correct resolution, but sometimes it fails. So manually check the resolution the computer is sending and try to set it manually. My Sharp Roku TV works fine when I connect my work laptop and offers 4K/30 resolution. But it has a high end graphics card that lower cost computers won't have.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
If that were the case, then wouldn't any tv with HDMI in not display it? While my Roku TV is 4k, I know the pc is not. Yet if I plug the PC into other TVs with HDMI and a 1080 display it will work fine.