PC no longer identifying 3 other monitors. Thoughts?
Solution 1:
Something changed in the Ubuntu OS or the BIOS setup. A driver update, multi-monitor was turned off in the BIOS setup, an upgrade messed with a config file, new driver version defaults to single monitor configuration, proprietary nVidia driver kick out by nouveau open-source nVidia driver.
Try nvidia-settings, Look at the monitors (or screens) section. Try reinstalling the correct nVidia driver apt install nvidia-driver nvidia-kernel-dkms --reinstall.
Follow the onscreen instructions. If that doesn't work, I'll eat my shorts!