Firefox just updated itself to version 56.0, and where my Xmarks add-on was working prior, now it does not. The icon is grayed-out and when I select "Synchronize Now", the little sync window pops up, but nothing happens and it locks up my browser to the point that I have to restart it. I am aware that there is supposed to be some new add-on functionality in Firefox v57+, but that would not appear to be the problem in this case.
Does anyone have any insight into what the issue could be? Even better, anyone know a fix?