whenever I try to save the game, I get a "fail to save game" message.
So far I tried:
1. run as administrator
2. change firewall settings
3. change user ownership of both GOG folder and Installation folder
4. reinstalled the game
5. repeated the other steps after reinstalling failed (and attempted after each one of them)

I contacted GOG support a week ago, but I have yet to get a response


other than that, the game works perfectly well

running on windows 10

I cannot believe nobody has answered this question since 2020!!!
likely on Windows 10 it is Ransomware Protection is enabled. you can go into Defender settings and switch it off. likely you can check your "block history" if you play online at all times and just set it to ignore this game if you wish to leave RP on.