Hi, I got interested in trying out KDE. I've been running XFCE4 before. I have two 1080p monitors that I've been using on XFCE4 with XFCE4's default display management tool. When I switched to KDE, it could not extend and use two monitors. When I try to enable it, it says:

Sorry, your configuration could not be applied.

Common reasons are that the overall screen size is too big, or you enabled more displays than supported by your GPU.

I am running Nvidia Geforce 1080 with proprietary Nvidia drivers on Xorg version of KDE.

Image: https://i.imgur.com/Sf3mzVs.png

Clearly I must have missed something. I think KDE mis-read Nvidia's settings or something. How do I fix it and make it to use both monitors?

I've fixed the problem. It was not KDE at all. I came back to XFCE4 and it refused to use second display. After a hour of troubleshooting, it appears that my display malfunctioned and I couldn't configure monitor's settings using monitor's buttons nor I can turn it off using power button. I unplugged and plugged it back in and it's now reset and XFCE4 and KDE now detects and uses it properly.