Simple flat model yet I cannot get an area to refill after accidentally deleting the face

OakmontC2.skp (996.1 KB)

Would really appreciate some help here as I have wasted hours trying to get this face to refill that is transparent currently. I have tried redrawing the entire thing and it still will not fill for some reason. The model is completely flat so I cannot understand why this non filled plane is empty.

Your model isn’t completely flat, orbit around and look underneath, however that bit isn’t causing the problem.
In each case where the faces failed to form there are edges extending into the space, By removing them or isolating them(by grouping) the faces will form.
OakmontC2Box.skp (847.4 KB)