Now, in Fx 56.0.1 (at least 64 bit, Win10) the version Tree style tab 0.19.2017090601 is works (show in https://cup.aihedy.com/en/firefox/addon/tree-style-tab/versions/ ). But 2.x.x is "not compatible" yet.

But in Fx Developer Edition (57.0b11) Tree Style Tabs 2.0.8 is works (with new style of tabs by default).