Just put in a brand new XFX RX 580 XXX Edition, 3 DP ports. Trying to run triple monitor set up, 1st and 3rd DP ports connected to 27" Asus and 24" Asus monitors respectively. These two monitors work correctly, recognize in Windows, extend, etc. The second port is DP connected with a DP to HDMI cable to my 40" TV, yet it does not recognize no matter what I attempt to do. Does this card truly not run 3 monitors from 3 ports? Thanks!
that HDMI adapter must be an "ACTIVE" adapter. If it is not then that is likely your issue. I have seen claims of people buying ones from eBay that claim they are active but still don't work, so buy be ware and don't assume it is something else if you think the one you have is claimed to be active. If you can pick one up locally retail, I would recommend you do that. I know Micro Center carries them in house.