I've been trying to play multiplayer with my family, but we all have this issue where we can't press the End Turn button. We click on it and nothing happens. How can we fix this?

I don't have it in front of me right now, but I remember having the same problem and I think a compatibility mode either caused it or solved it.

Sorry to be so vague. It's been a long time.

Another thing you try would be to ALT+TAB out of it and then ALT+TAB back in to see if you can click End Turn.

I found the multiplayer to be completely unplayable. Messages appear and disappear too fast to read. And multiplayer wasn't syncing right (I remember that was a problem with the original game, but my attempts were ridiculously bad). I played with auto battles and it just wasn't super fun that way.