I have a very strange problem with the second DVI port on my GeForce 5601Ti with ubuntu.
Both xrandr and nvidia control panel show second monitor disconnected (monitor and cable verified on first DVI port), even with clean install of OS (even tried different versions of Ubuntu).
Both DVI ports and monitors used to work fine on 16.04 and 18.04. Then something happen and the second DVI port shows disconnected.
After trying EVERYTHING I could think of (and everything suggested on various forums), I thought the card was broken and purchased a new (a 1050Ti) but still have the same problem. I’ve booted on a live-CD with both 16.04 and 18.10 to test with a clean install but both cards show disconnected on the second port (DVI on the 560 and HDMI on the 1050). The motherboard is a MSI B350.