I've used this extension previously on Fennec, where it worked smoothly. After moving to IronFox I've noticed that when visiting a blacklisted page, the background becomes blurred, but Vergil never comes to save the day, the page is just stuck in a blurred state.
I'd be happy to provide any debugging info that might help with reproducing or fixing the issue, but as I have zero experience with browser extension development I simply have no idea what might ne needed.