Look for the Document Preferences dropdown (gear icon) or right-click inside any citation. Select "Relink Citations..."
For anyone writing a thesis, journal article, or book, Zotero is an indispensable tool. It manages your references and, via its word processor plugins (Microsoft Word, Google Docs, LibreOffice), inserts in-text citations and bibliographies automatically. how to relink citations in zotero
When all else fails, remember that a Zotero citation is just a pointer. If the pointer is irreparably broken, you can still manually re-insert the citation. It's tedious, but it's faster than rewriting your bibliography from scratch. Look for the Document Preferences dropdown (gear icon)