Out of the 6 HD monitors that make up the display, only 2 were allowing me to use the FHD 1080p resolution. The other 4 were listed as “Generic Non-PnP Monitor” on the display properties.
I reached out to AMD (the graphics card manufacturer) and the DisplayPort to VGA adapter manufacturer (a Chinese company). After spending a lot of time messing with a ton of different suggestions from the manufacturers and on various forums, the problem turned out to be the VGA cables.
In a race to the bottom some of these cable manufacturers leave out expensive copper wire that they don’t think people will miss! The one that is missing in my case is the SDA (pin 12) which is apparently responsible for “plug and play” detection of the monitor’s capabilities.
Hopefully this will save you some time … swapping the cable out for one you know works is the easiest way to troubleshoot this IMHO. And if you buy cables you should either check for continuity through all 15 pins (and the chassis) or hook it up to make sure you have all the features you are expecting.