I am having a similar problem. I can not get word to communicate with Zotero, its says I should open firefox or zotero, so I logged into zoter0 through firefox and still wouldn't work. I can't get the small box zotero to open up either, I have to log into the website. My Zotero is completely screwed up after the last updates. I downloaded the stand alone several times and can not get it to work! Please let me know how to get zotero to start running properly again. Thank you
Also, when I go to the Zotero add on in Firefox it says under the general status that Zotero is currently unavailable, I seemingly have no way to change that.
https://www.zotero.org/blog/zotero-5-and-firefox-faq/