I took the PC to the office, connected it to my AOC monitor via Display Port, and all was good, finished configuring Win10 etc. Tried connecting the PC to the monitor via HDMI as well, all was good! Took the PC back to living room. Again, just got the initial DELL screen, black screen afterwards. I brought the office AOC monitor to my living room, connected it to the DP and the TV to the HDMI port of the DELL, turned it on and it worked, I had signal on both screens. The resolution on the TV was automatically adjusted to the recommended 3840x2160 with a 29,970 Hz refresh rate and RGB color format.