Blender; Does anyone know what could be causing this issue with loops and subdividing?

LadyPoro

I'm using Blender to create this. I'm just curious of what the issue could be? It's nothing I can't easily recreate though so no worries if there's no answer.
The normals are the correct way, I've tried creating the edges by hand by using the vertex around the edges (it does create new edges- but the face is still disappears in ZBrush even though the normals are the right way). I've deleted the top row of faces and created a new one, but it still stays the same. It just won't allow any subdividing or loopcuts. 

Any ideas of what could have gone wrong here?

Thanks!

Shadowstep

That top face is an N-gon. Delete it, select the top edge loop, and then Ctrl+F -> Grid Fill.

LadyPoro

Shadowstep said:

That top face is an N-gon. Delete it, select the top edge loop, and then Ctrl+F -> Grid Fill.

Thank you!