I've been using two monitors for a while, but one day it suddenly stopped working. I did not update or change anything that I'm aware of. I've tested with another monitor, but my computer is refusing to use more than my main monitor. I'm using Windows 10 and 2 x AMD Radeon HD 7800, with one monitor connected to each card. Going to windows settings and choosing display is not showing any option to choose or identify any additional monitors, like it used to do. What to do?