Related, but just hanging this on here. As the default (as installed) security of distributions has improved, so have the amount of headaches when trying to use tools like this increased. For decades, when I've had issues like this is not been because of a LAN firewall issue, and so now my first thought is never been, "I should check the firewall," when it should.
Sadly, firewall info is almost always locked down so that apps can't even check by themselves and provide helpful hints to users.
Anyway, it's been a hard lesson for me to learn, for some reason. I need to practice my mantra: it's always the firewall.