I have an RX 590, I have been using this dual monitor setup with no issues, but after installing driver updates, my seconds monitor stays in standby and doesn;t light up and is not detected by the system.
Main Monitor: ViewSonic VX3276 4K
Secondary Monitor: Dell 2001FP
If I ALT+R and select "enable clone" in the top right, the 2ndary monitor lights up and clones the main display, so this is not an issue with a bad monitor
In fact I can then select "Extend these displays" in the windows control panel and the computer starts using both monitors, but switching users on the computer or rebooting seems to lose the secondary monitor, at least some of the time.
I tried uninstalling the drivers (use the AMD clean install that uses safe mode) and reinstalling but the problem remains.
I also have another issue that I'll post in a separate thread where the main monitor goes dim when I extend displays.