Zotero not working in google docs


Zotero is not working in google docs.
I'm using google docs with a friend. We share an online library in zotero.
It worked until yesterday.
When I try to add a citation - Error message comes up.
I installed/deinstalled zotero a few times -> still doesn't work
I tried in a new google docs document -> still doesn't work
I use Firefox; I added plugin for word of course.

I have a windows pc.

Somebody had the same problem?

Thankful for any help.
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