After checking, seems that the extensions is not even able to display some of it's elements, nothing happens when I try to click on buttons/elements("Check for filter updates" and "All filters" for example) that are still shown.
Unfortunately it seems that versions above version 2.7.3 are not working in my Firefox browser.
Win7 x64, Firefox 61.0.2
I have tried installing it in private mode with no luck.
You can also see that settings page is practically blank in new versions.