I have the same problem as others where only one screen out a 3-screen setup works. I have uninstalled AMD drivers and the 3 monitors work with the basic Microsoft driver. However with the latest AMD driver two of the screens are black. They keep trying to activate but never display the image. The problem seems to be with 15.7.1 because I downgraded to Windows 8.1 but had the same problem. Everything worked perfectly until upgrade to Windows 10 forced upgrade to 15.7.1.
I will try and raise a support request direct to AMD or is this the correct forum?
Fixed. I unplugged and replugged the DisplayPort cable from the PC while it was running and all three monitors turned on and operated correctly.