Rendering Android native view with OpenGL

I'm trying to render a Android native view, wherein I render something through OpenGL.

I can see the native view's background colour, so I know the view is being rendered, however, the stuff I'm trying to render through OpenGL is not rendering, and the part of the view becomes transparent or perhaps behind Unity, I don't know, but it isn't showing. I'm playing some sound also, so I know the code is actually running.

So question is, do I need to do something special to get Unity to render this? Or do I need Unity pro to get access to render like this from native android code?