Hi, have the same problem. I have a AMD R9 270x. I have windows 10 pro, last driver installed, 3 monitors connected by:
1 hdmi monitor to DVI (graphics card)
1 hdmi monitor to HDMI
1 hdmi monitor to card's dvi port with adapter (ACTIVE)
I tried everything i could find in internet and nothing worked. Here are some pictures of the problem:
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As you can see, third monitor is not active, but connected by HDMI to DVI with an active adapter.
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I dont know why i cant activate this monitor. When i disconnect one of the others, this one turns on. The problem is that i cant set 3 monitors at once.
Finally, here is the AMD settings, not detecting the third display.
I really hope you can help me, i think may be is a issue of windows version? i dont know. PLEASE HELP and excuse me for my lack of english.