I recently had a problem with a Firefox add-on called "Split Browser" preventing me from accessing and using ZOTERO. In the process I disabled all of my add-ons and reactivated them one by one. That was the only one I could find that prevented me from accessing and using ZOTERO simply by virtue of being enabled. I do not know whether specific functions of other add-ons cause similar problems or not.

This is a relatively minor but annoying inconvenience. It would be useful to be able to use ZOTERO while simultaneously browsing multiple pages using SPLIT BROWSER.

Do you have a process whereby compatibility of your program with other add-ons can be verified in advance?

Yes, exactly. I should have seen it earlier. Anyway, problem solved. Thank you.