I recently upgraded from 15.10 to 16.04 via dist-upgrade. Immediately afterwards, my second monitor stopped working. I am using an AMD 7850 APU, and both monitors are plugged in to the motherboard - One is connected with an HDMI, and one is connected with a DVI. The monitor with the DVI cord is not displaying.
When I open "Displays" in the system settings, both monitors are shown as being detected. I tried disabling and re-enabling the blank monitor with no luck.