I am currently running Debian Sid 64bit using the latest Sid-repo Iceweasel (Firefox) browser. I also use Zotero, which is a great FOSS bibliographical software program backed by George Mason University (i.e. EndNote replacement for those who care about free software and digital ethics). There is a standalone version, but I have chosen to use the Firefox/Iceweasel version so that it “resides in” Firefox.
Many times it does not open with the keyboard shortcut (Ctrl+Shift+Z). The fix is simple: Go to Firefox panel –> Add-ons –> then go to Zotero. Click Disable and then Enable (you don’t have to restart Firefox, or at least I don’t).
While I’m at it. If you want to get rid of the bottom Add-ons pane for Firefox, I think you have to go to Zotero’s preferences and disable the add-on icon (changing it to “None”). Otherwise, the add-on bar might keep on popping up.