Plutonium

@MrMorningstar666 This means the host either did something wrong or has something still blocking the connection (firewall, antivirus firewall etc.) Make sure you follow the Custom game with friends guide correctly and your router/firewall/antivirus firewall is not blocking the connection.

@MrMorningstar666 your friend/the host may have to port forward, check this guide: https://forum.plutonium.pw/topic/7/custom-games-with-friends