I’m new and I’m an happy owner of the UD-ULTC4K connected to a Lenovo X1 Carbon 6th Gen. I’m switching to a 3 monitors setup keeing the laptop lid closed. I have 2 21:9 2560x1080 monitors and 1 4K monitor.
The 4K monitor is connected to the upper DP, one 21:9 monitor is connected through HDMI Alt Mode and the other is connected through the second DP. This last monitor isn’t working, it seems to be recognized but no image is shown and keeps turning on and off. I’ve already followed the suggestions on https://support.plugable.com/t/displayport-not-working/11424 but without success. If I switch the ports it seems that only the upper one is working (the 21:9 turns on, but the 4k dies). I have bought another cable that should arrive soon, but at this time I don’t think the problem is cable related.