I have 2 monitors connect to my R9 290 graphic card via mDP (Dell U2417H) and HDMI (Dell SE2717H)
I can't access to eyefinity advance setup cause It wasn't there (only the quick setup is available). I have update the driver to latest back and forth but still no hope.
Looking for an Answer for my issue I see yours. I had to uninstall and reinstall and it fixed the issue you are having. The only thing is it won't open The Advanced setup which is the problem I am having. as well as my screens are not aligning correctly.