I open a new drawing by clicking the New icon on the standard.  When the new document opens, the only icons showing as available in the Features toolbar are: Extruded Boss/Base, Revolved Base, and Reference Geometry.  All of the other Features toolbar icons are grayed out.  When I go into Insert>Customize Menu I find the boxes for both available icons and grayed out icons to be checked.  The grayed out icons shown on the Features toolbar are also grayed out in Insert>Customize Menu.  How can I restore these grayed-out Features toolbar icons?