Why cant i extrude/thicken/Offset face this side wall (SEE IN PICTURE)

[Warfield7YVQN]

Why cant i extrude/thicken this side wall (SEE IN PICTURE PNG)

Im working with Fusion 360.

Here is the file.

Thanks

[Warfield7YVQN]

Why cant i extrude/thicken this side wall (SEE IN PICTURE PNG)

Im working with Fusion 360.

Here is the file.

Thanks

[jeff_strater]

please see the response I posted in this other thread:  why-cant-i-extrude-thicken-this-side-wall-see-in-picture