They'll say "Updating" while the citation dialog is open.
Make sure the citation dialog isn't just appearing behind your other windows. That's the most likely cause of this. The citation dialog window is part of the Zotero app. Restarting Zotero may cause it to start appearing in front.
If you're sure it's not that, try disabling any other browser extensions and reloading Google Docs. If that doesn't help, restart your browser and Zotero and provide Debug IDs (different from a Report ID) from Zotero and from the Zotero Connector for an attempt that doesn't work.
Upgrade Storage
Make sure the citation dialog isn't just appearing behind your other windows. That's the most likely cause of this. The citation dialog window is part of the Zotero app. Restarting Zotero may cause it to start appearing in front.
If you're sure it's not that, try disabling any other browser extensions and reloading Google Docs. If that doesn't help, restart your browser and Zotero and provide Debug IDs (different from a Report ID) from Zotero and from the Zotero Connector for an attempt that doesn't work.