Stuck on "Zotero is updating your document"

Started having Zotero Google Docs integration getting stuck on "Zotero is updating your document. / Please wait…".
This happens after performing an operation like adding a citation or editing citation, and even editing a citation, then cancelling the operation.

There are no background popups for Zotero or the browser.
Zotero 9.0.4
Firefox 151.0.1

This attempted:
* Restart Zotero.
* Restart Firefox.
* Clear all Google cookies.
* Restart the computer...

Debug ID: D1736275613

Checking the browser plugin settings, in the "Advanced" section an error is displayed:

[JavaScript Error: "Zotero.GoogleDocs.UI.activate is not a function
activate@moz-extension://6c61d2f9-a1d8-491b-937b-a6fe875a31a9/zotero-google-docs-integration/client.js:150:24
call@moz-extension://6c61d2f9-a1d8-491b-937b-a6fe875a31a9/zotero-google-docs-integration/client.js:67:32
init/<@moz-extension://6c61d2f9-a1d8-491b-937b-a6fe875a31a9/zotero-google-docs-integration/googleDocs.js:77:16
init/</client.call@moz-extension://6c61d2f9-a1d8-491b-937b-a6fe875a31a9/integration/connectorIntegration.js:57:12
respond@moz-extension://6c61d2f9-a1d8-491b-937b-a6fe875a31a9/integration/connectorIntegration.js:106:18
" {file: "[object Object]"}]
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