Multiplayer not working

[undefik]

I have been unable to play a multiplayer game with my nephew. We tried starting a game on either machine, both directly on LAN and over a ZeroTier network (whose IP address swas almost always shown in the multiplayer menu on one of the machines), via the menu and via the connect console command, but the connecting machine always responded with HOST_ERROR: CL_CONNECT: CONNECT FAILED.

Both machines are running Ironwail 0.7.0 with the Id1 folder taken from a ripped WinQuake CD install.