How this even should work?
"Tuxler Chrome Application"
This addon requires Tuxler Application to work.
"After installing this extension you will be directed to Application installation process." and you can't do a sh without it.
and another one: "Tuxler Chrome Application is requied to start Tuxler Plugin"....This is FIREFOX, not Chrome!
Firefox/76.0.1 == Imo it looks overrated and I suppose, that owner(s) are giving bigger stars than it actually needs.
This addon didn't work for me without that another thingy. I'm disappointed.
Check permissions and "Make sure you trust it before installing."