An error occurred while saving the commentmrobrian commented
I tried the fixes I saw here, and nothing worked, but then when I had the same problem with WoWMatrix, it actually gave me the hint on how to fix it:
Go to your WoW install folder. It's probably under Program File (x86), and for me I play on PTR and retail, so I had subfolders.
You might have a "World of Warcraft Launcher.exe" file instead of WoW.exe. Make a COPY of the launcher file and name it WoW.exe.
The Twitch client should now see your game, and it shouldn't affect anything else.