Why won't an app show up in screen overlay?

[AC Question]

I'm trying to do a video call with a good friend of mine. At first I tried using Hangouts but screen overlay pops up, when I click on it Hangouts doesn't pop up on the list. I thought it might be the app so I downloaded an app called ooVoo and it still didn't show up and I'm starting to get frustrated.

 

[ManiacJoe]

You need to temporarily stop, or uninstall, the app acting as the overlay. Common apps are
screen dimmers (Lux, Twilight)
sliding menus and trays
Facebook bubbles
multiple apps from Cheetah Mobile.

See if this thread helps:
http://forums.androidcentral.com/sa...often-some-apps-what-how-properly-select.html