I'm setting up a brand new WIN10 + FIREFOX 72 machine (moving from a working WIN 7 + FIREFOX 72 machine) where the addon was working perfectly. I initially wasn't working on the new machine, but I noticed the developer's comment about FIREFOX 72. I followed his instructions and it's now. To repeat his instructions ... my understanding is ... if addon was installed >>before<< upgrading to FIREFOX 72
1. remove addon
2. restart FIREFOX 72 twice
3. reinstall addon
4. (small addition I added) close and restart FIREFOX 72

Love the addon. Hated the thought of losing it on my new machine.