Proxies don't work with new Mac user account
After having my Zotero proxies working nicely for a couple of months, I had to switch to a new user account on my Mac. I reinstalled Firefox and Zotero and copied all the Firefox application support files over to the new account. Now Zotero is working normally except that none of my proxies are functioning. They are all present in preferences, but they have no effect. I tried deleting one and recreating it, but it didn't help.