Faces missing in faceselect mode

Support Basics & Interface
1

I’m having a problem with a project.

When I enter faceselct mode some of the faces of my model are missing.
What does this mean and how can I fix it?

2

It means something you did in the modelling either left out faces (Extrude only edges or only verts) or deleted faces (X=Faces, X=Edges).
Select the 4 verts or edges that enclose the face and hit F to make a face.

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3

then use [j] (join triangular faces) to convert the tris back to quads.

~Delta

4

FaceSelect mode is normal sensitive too. That is, it only shows the face that have normals facing the viewport.
So you problem might be caused by normals not pointing in the correct direction.
Just select the offending faces and hit Ctrl-N.

Martin