So I have intermittent issues with my two Samsung 28" UHD 4k Freesync monitors and my Radeon 390X video card on Windows 10 x64.
Both monitors are connected by DisplayPort and FreeSync is turned on on both monitors.
My PC is on 24x7 usually - I turn the monitors off typically, and most of the time they turn back on and apart from some window resizing they work fine.
Every now and then though (and often enough to be extremely annoying) - only one monitor will turn on - the other will go blank.
I can go into Windows Display settings and the monitor is listed but Multiple Displays is set to 'Display Monitor 1 only' and not 'Extend desktop'.
If I attempt to 'Extend Desktop' to the monitor it fails. AMD drivers fail to list the monitor and nothing I do seems to bring it back - the only fix I've found that works reliably is to reboot, then select 'Extend Desktop' once it's rebooted.
I've had varying success with plugging the monitor into another DisplayPort port on my video card - it's worked sometimes, but not all the time. I've also had varying success with turning FreeSync off in my Samsung monitor control panel - sometimes this will work and both monitors will turn on - othertimes it will just cause the monitor to come on and the other one to go off.
Also if I turn the monitor off that IS working then the other one wakes up and works fine.
I've tried every display driver and not noticed any difference - 15.12, 16.1, 16.2, 16.3
It's been the same with past drivers too - I've been having the issue for a while but finally gotten to the point where I'm just so frustrated with it.
I have a similar problem. I have a 4 monitor setup. Three of my monitors are all 24" ASUS 1080P, same make and model. Recently I added an LG 27UM88W UHD 4K monitor for photo and video editing. I have 2 AMD R9 Fury-X graphic cards in my system. They are not setup in a crossfire configuration (in X-Fire, the output ports are defeated on the second card). I have installed the latest AMD Crimson ReLive Edition 17.4.4 drivers. Unfortunately, the LG monitor on occasion fails to "Wake Up" from sleep, while the 3 ASUS monitors do not have this issue. I am currently running Windows 10 64-bit, and recently upgraded to the Windows 10 Creators edition. I have installed the latest drivers Crimson ReLive Edition 17.4.4. But I continue to have issue with the LG display after all monitors go dark. Anyone that may be able to suggest a workaround, or solution your sage advice would be appreciated!