I have a 5k iMac, the most recent one, which I've been using since December along with a BenQ external monitor, and both have been working fine. Then yesterday I go away for a little while. And then when I wake up my iMac, put in the password, the second screen doesn't wake up alongside it. I've tried NVRAM reset, tried the other power cord reset. The monitor isn't dead either. It's in sleep mode, with the yellow light flashing. I have it plugged in via a DVI to Mini D port adapter. If I remove the cable from the iMac and then insert it back into the computer, no response whatsoever. If I detach the dvi side of the adapter from the dvi cable, then the light goes green for a while. I'll assume that means the adapter works fine - unless its the mini displayport side of it that's broken. I have nothing else to test it on to know for sure. The "find screens" doesn't do a thing when I click on it. From the monitors menu -> colors, theres a profile for a BenQ monitor, but I assume its just a history profile, not the iMac telling me it recognize the presence of a second monitor. The suddenness of this has got me stumped. Any help appreciated.