MJVandershonk: I still have the issue. I contacted GOG support about it a couple of weeks ago and they replied quickly asking for logs, i've sent them but haven't recieved a response back as of yet.
Lexor: Can you check on your system firewall what remote IP/port your game is trying to contact before the multiplayer mode fails?
I'm seeing several connections:
galaxycommunications
UDP OUT 77.79.249.151:514
TCP OUT 199.232.57.55:443
TCP OUT 199.232.57.55:443 (from different source address)
Both TCP are starting and stopping automaticaly
Galaxy Overlay
TCP OUT 199.232.57.55:443
Iron harvest
TCP OUT 35.227.230.186:443
TCP OUT 34.107.172.168:443
TCP OUT 34.111.113.40:443
TCP OUT 207.154.210.110:443
Just did a ping test using my router diagnostics on some of these and they look fine, no issues, I think the overlay one has another connection that blinks on and off on game start.