Be sure to always say exactly what you're referring to — there are a lot of ways to use Zotero. This is about Google Docs integration? How big is the document? Does it work in a new document?
Restart your browser and Zotero and try again. If you're still having trouble, we'd want a Debug ID (different from a Report ID) from Zotero for an attempt to insert a citation.
Upgrade Storage
Restart your browser and Zotero and try again. If you're still having trouble, we'd want a Debug ID (different from a Report ID) from Zotero for an attempt to insert a citation.