Try getting rid of the accessory elements (sunshade/canopies?) first before trying to offset it and then re-apply them after..
They might be constraining or restricting it.
You might also have to (temporarily remove the door panel as well;
...although I suspect your surest solution is simply to redraw it.
The Curtain wall tool does that sometimes, where beyond a certain point you can no longer edit it (particularly the reference lines and extruding and stretching boundaries), and it registers as a buggy or incorrect element (you know this when your ArchiCAD crashes and upon restart it informs you that it found some errors in an element which was automatically deleted after a file recovery audit, and then you realize it was the curtain wall. Very annoying. They should give you the option to delete it manually so that you can at least re-draw it using the buggy one as a reference).
I strongly suspect in your case you simply just have to redraw it to the new boundary.
Once it's no longer responding to Edit commands, it's probably too late.
