Hello AlekOkK, are you trying to do a simple LAN game or LAN Co op game? I have my two systems configured on my LAN to play again each other. Two separate games of Red Alert 3 *store bought*. I am able to connect to my other computer system in LAN without any issues and have played 1vs1 etc without any issues. But when I connect both of them online to Revora and try to connect the two systems to play a co op campaign I get that error above, network error connection failed 1-2 even though I see both computers in the lobby and get all they way past all the videos to start the game and then I get the error. So if you get any new info on your issue I hope it will also fix my issue too. All my internal firewalls are off and I did not do any port forwarding since it work flawlessly via LAN.
ciao