I'm well aware of version 7 not yet working properly on FireFox 57. That is not the problem here. I have version 6.3.3 installed on FireFox 56. Updates are switched completely off. It worked fine until the middle of the night a few days ago. It finished the current download, then suddenly disappeared and the animated icon will not come back regardless of any setting. It has simply ceased to function, and not coincident to any "quantum" related update/upgrade, or any update/upgrade at all whatsoever. It has become painfully obvious that you are connecting to the program behind our backs in a manner you have not previously disclosed. There's no valid reason for it to suddenly stop working when no updates/upgrades have even occurred.... Killswitch much? Of course you do.