I was looking at display settings on AMD Radeon settings, when I accidentally clicked on Enable Clone. Whatever, just disable it, right? No, it seems to have completely messed up my second monitor. It still works, as if I re-enable cloning, it still works, but whenever I disable it, it goes back off. Windows recognizes it... Sort of? Everything's greyed out, and I can't really do much, but Radeon settings doesn't seem to recognize it at all. Nothing seems to work, so it's up to you, random strangers on the internet.
I had this problem too. I solved it by manually changing my displays back to extend these displays. Hopefully this helps.
I know this is a bit of a necropost, but I found the solution:
Go into Windows Display settings, select the disabled monitor and scroll to the bottom.
Under Multiple Displays, change the drop-down from "Disable this display" to "Extend desktop to this display".
Use these steps if you are using windows 10 and you are using the latest version of AMD Radeon Settings
Step 1: Turn off computer
Step 2: Boot it up again
Step 3: Enter in password if you have one
Step 4: Press the windows key on your keyboard
Step 5: Type in amd
Step 6: Press enter on your keyboard
Step 7: Press Tab on your keyboard 15 times
Step 8: Press enter on your keyboard
Step 9: Press Tab on your keyboard 7 times
Step 10: Press enter on your keyboard
Step 11: Press enter on your keyboard
You should be good to go from here hopefully
Hope this worked for you
I ran into the same issue. I have one DP to a VGA and one hdmi to a hdmi. it always puts the vga to primary and clone.
If I use DV to DV monitor and keep hdmi, it works fine.