Thanks so much for the info. I have very limited knowledge of this stuff, but I will be taking the info you gave me, and searching the info you provided, in order to try and learn what you are talking about. In the meantime, despite not being able to connect to IPv6, Eddie is running just fine and I have been happy with it for several years now. Great support, not only from staff, but from users as well.
I try to re-explain.
You can connect to AirVPN servers via IPv4 OR IPv6. This is controlled by the option "Settings -> Networking -> Internet protocol used for connection". To connect via IPv6, you need to have IPv6 enabled on your network adapter, and your ISP support it (so, you need to have IPv6 connectivity WITHOUT the VPN here: http://ipv6-test.com/). But you have also IPv6 disabled on your network adapter, so try to run in terminal
networksetup -getinfo Ethernet
and if report "IPv6: Off", try to run
networksetup -setv6automatic Ethernet
to re-enable it.
I suggest to leave "Settings -> Networking -> Internet protocol used for connection" at "IPv4, IPv6" (the default).