I'm trying to play on a local network with 2 players using our local IPs. Whenever one of us tries to connect to the server the other is hosting it says "game in progress", which it isn't.  It seems to recognize the existence of the server since trying to connect without it yields the "timeout" error, but it won't let either of us join. Do ports have to be open no matter whether you're using a local or external IP? We gave all the firewall permissions it asked for and are using the latest GOG version. I'm not sure if it's compatible since it doesn't tell you the current version like steam does, but it seemed to install without errors.

"game in progress" is usually resolved by restarting the game on both sides - it's only shown if the game returns a specific response.

GOG should work fine. Should not have to open ports if it's on LAN and you are using local IPs.

Also, for clarity, this is what you should be seeing as host (left) and client (right) prior to clicking Join on client side

My mistake, I did try connecting after hitting start. I was sure I had tried it on that screen too, but apparently I imagined that.

Thanks for the help, we're having a lot of fun playing this right now :)