After Firefox/Zotero update, error message "could not complete"

I just updated Firefox or Zotero, as prompted by the system (can't remember which one updated, but I think the purpose was to incorporate new plug-ins) and when I now restart Firefox (with Word closed), I get:

Zotero Word Integration could not complete installation because an error occurred. Please ensure that Word is closed, and then restart Firefox.

ANY THOUGHTS OR SUGGESTIONS (aimed at very-low-level technoid) ON HOW TO FIX?

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