Thank you, eduzs & Guessed, for your replies.
eduzs: I've tried opening the file both via the File-Open menu and via Windows Explorer (both by double-clicking and by right-click/open). Unfortunately, either way, although the document is open on my screen, it doesn't appear in the VBA editor list and none of the macros can be run or edited. I do see them, though, in the list of macros when I click on "Macros" in the "Developer" tab...I just can't do anything with them.
Guessed: It's true that I'm opening a file that's stored on OneDrive, but other files (earlier iterations of this project saved under different names, also on OneDrive) open fine, with all macros intact. Regarding your question about add-ins, the macros are contained in the .docm and not in an add-in. (I'm not sophisticated enough in VBA to work with add-ins.
) And, unfortunately, I know nothing at all about xml. (In fact, I just had to look it up online to find out what it is.)