U>Unwrap isn't working for certain faces

I have a very strange problem here. It doesn’t matter what I do, certain faces refuse to unwrap using U > Unwrap. If I choose any of the other unwrap modes like smart UV project, project from view etc it works fine. Go back to Unwrap, The UVs just stay where they are.
-None of the UV’s are pinned
-Some faces on the model unwrap perfectly, others don’t.
-I exported the file as an OBJ, imported it into a new blend, and the same thing happens.
-I reset user interface, and then appended the object into a new file. No change
I’ve tried it on another computer. Same problem.
I’m using Blender 2.79b

These are the faces that do not unwrap:

It looks like it was a silly mistake on my part. Those faces were solid, as in, as soon as I deleted the underside of the stove plates for example, or created seams, using E- Mark Seam it worked.