How to play Heroes of Might and Magic III online via Hamachi?

Hi everyone. I'm not very original – I came here with my own problem and a request for help. We're trying to play with a friend over the network (same provider – Domolik), both of us have the same version of Hamachi, we connect to the network, ping each other, and see each other. Firewalls and antivirus programs are disabled. She starts the game, creates a server, I join, I see it, I try to connect, but it says "Session interrupted, please try again." We have the same versions (when they were different, it said "Sorry, different versions, nothing I can do..."). This problem occurs regardless of who creates the server. We both have EVERYTHING turned off (I can post screenshots if needed), but neither of us can join the game. We tried playing without Hamachi (Game Spy Arcade) – the same result. There, we can't join each other's rooms, the option doesn't even light up. (There, after joining a room, it's like you're playing – the program automatically starts the game and creates the server and sets everything up, you just press a button and you're in the game). What could be causing this, at least? Could our network, the provider, be blocking it? It's a dedicated, high-speed network. My friend doesn't have an unlimited data plan. Could that be the problem? We're desperate. We don't know what to even guess, what's the problem? Help!