Why can't I run 2 WoW instances?

Apparently people have no problem running multiple instances of WoW but I do.. apparently you can open up to 4 instances of WoW on Darkheal's Warmane Launcher so I go to open up another instance of WoW when i'm already playing in 1 instance and it opens but all I can see is my desktop.. I can hear the game sounds but it just shows my desktop. The original WoW window will open just fine.

Here's a screenshot of what it looks like when I try to run 2 WoW windows, 1 of them works and 1 of them just displays the desktop and only plays the sounds... http://i.imgur.com/3IPF6ML.png

I was hoping someone could help me get two windows of WoW working..

You will need a separate account for each instance. So, if you are running on your main account, you will need another account to run another toon at the same time. I usually do this when I am lvling, and I need some protection against gankers.

The same thing happened to me after I update my windows 10 1511 into windows 10 1607. The only solution i came up with was simply using window mode. probably somebody can shed some light into this issue (open multiple account with full screen).