Slitherine

hello, i am trying to set up multiplayer with my dad since he played the game on disk originally and we both rebought it on steam, we are trying to play multiplayer, got all the logins and everything working fine. however, when i try to play it works fine but when he tries to accept a challenge or take his turn (basically opening the scenario) the game crashed to desktop with no error message

anyone have a clue? i can provide anything if requested

two different serial numbers and accounts?