My phonebook was in the _hiddenPbk folder, and empty (as suspected; NordVPN uses its own software/TAP driver) so no luck, but thanks for the suggestion.
Please try this suggestion I posted in the News & Bulletins section.
I'm really curious if it will work.
To follow on from Howard, the correct string should be: 123.45.6.7 We've updated the OP to reflect this as well.
forums.frontier.co.uk
Upon a bit more investigation, I did notice one thing:
When connecting without the VPN on, on the first screen if I go to Options / Network, my Local address and internet address are set right.
HOWEVER, when connecting with the VPN active, my internet address is then also listed as my LAN address, so it would be impossible for anything to connect to me that way. And I do get the feeling the Frontier servers are trying to connect, for some strange reason, because when I start the game with the VPN I can still connect to SOME things (like I can see my updated ARX from the previous session, commander name and location for the account I'm logged in with (I have two accounts), etc.
So clearly I'm connecting to the servers, but Social stays ghosted and I can't open a session (Open/PG/private) until the server connects to me. I'm not sure why it wants to connect to me, either. And since the vast majority of VPNs do not support port forwarding, it seems like it would NEVER work with a VPN since this has a specific port number it wants to connect to.
This is all recent changes, too: I've been playing over a VPN for years without an inkling of trouble.
Edit: looking more closely as I added that screenshot, I also notice UPNP was no longer listed as On, and router type changed from Port Restricted to Symmetric. And also (not in the screenshot) the MTU is set to 0 with VPN on.