I have a R9 380 and am running Windows 10 64
I had no problems running 3 monitors, with the 3rd going HDMI. I was having a display issue with some text on my second monitor, so I decided to update my Radeon driver. Well, now the 3rd monitor no longer will do anything more than 1920 x 1080.
I have uninstalled, reinstalled, rolled back to v18, v17, uninstalled entirely, and nothing helps. In fact, with NO software installed, that monitor would go to 2056 x whatever it was. Strange, right?
So, when it updated, I did notice that in settings, what used to say AMD FreeSync, now says Radeon FreeSync. I thought maybe rolling back versions would help, but no dice. Having 2 monitors at 2560 x 1440 and one at 1920 x 1080 is maddening.