Jut added this post
acedCreateEnhancedViewportOnDrop(Add a sheet view to current sheet of SheetSet) and you might guess where this is headed but they make Model Views layerstates hidden and left out the LayerStateMasks.Hidden for .NET.
Anyways a quick way to make them visible or editable through the UI with Layer State Manager
[CommandMethod("RemaskHiddenLayerstates")]
public void RemaskHiddenLayerstates()
{
var layMan = Db.LayerStateManager;
var names = layMan.GetLayerStateNames(true, false);
foreach (var name in names)
{
var lmask = layMan.GetLayerStateMask(name.ToString());
int numMask = Convert.ToInt32(lmask);
if (numMask > 32768)
{
numMask = numMask - 32768;
}
LayerStateMasks lsm = (LayerStateMasks) numMask;
layMan.SetLayerStateMask(name.ToString(), lsm);
}
}