A few of the possibilities:
Has anyone accessed this office library from a newer version of AC (e.g., AC 12)? The parts may have been converted to a format that your current version no longer recognizes. (I recommend that you have Office Lib 11, Office Lib 12, etc.)
AC could just have royally screwed up the GUID/name matching for the part.
If you do not have the command 'Open Object by Subtype...' in your File >Libraries and Objects submenu, use the Work Environment to get it there. (VERY annoying that GS took this command of the standard WE a few versions ago...it is the ONLY way to open objects that are not-placeable and yet are stored in an LCF file. Also, the only reasonable way to track down your problem.)
Invoke the command, and browse to the subtype corresponding to one of your missing-but-loaded parts. If you cannot figure out the subtype, place a new instance of the named part, open it and read off the subtype in the GDL editor.
You'll see the same name twice, most likely. One will be green, indicating it is loaded - a GUID will show along with the library path. The other will be red, indicating it is in the project, but is missing, but will show the GUID for that it expects that part to have.
Libary parts are supposed to be matched by GUID (the crazy long number string that you'll see), and if not (skipping the long story), then by text name. Clearly, the text name match is not happening for you. Seeing the GUID info above will help tech support figure out what's going on.
Screenshot of the dialog (but without a loaded/missing pair showing) attached.
HTH,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB