Thanks for that hint.
Ok now everything starts to make sense. Old FF plugin is not longer working but FF switched to the web standard that chrome is already using. Therefore Chrome extension should work with FF.
Unfortunately FF implementation is still not perfect and there is a bug in FF52. With FF53 everything works fine.

So the only solution for now if you want to use FF. Install FF53 which is not official available and use chrome plugin by installing it with chrome store foxified. I tested that and succesfully.:thumbup: