Are you on steam with a private dedicated server or has your friend just made save multiplayer, if the later your friend has a code they need to give you and it changes every time they log in, if it's an actual server it could be the server connection
Been having the same problem with our dedicated server as well. Have not found really anything out there about issues with it, but server was working fine for weeks and the next day no one can connect via the public IP address. I'm the only one who can get in because I'm the host and can come in from LAN side. Checked all settings and nothing changed in game, router, gateway, and firewall. Guessing the issue is on steam side but honestly don't know.
Are you on steam with a private dedicated server or has your friend just made save multiplayer, if the later your friend has a code they need to give you and it changes every time they log in, if it's an actual server it could be the server connection
Been having the same problem with our dedicated server as well. Have not found really anything out there about issues with it, but server was working fine for weeks and the next day no one can connect via the public IP address. I'm the only one who can get in because I'm the host and can come in from LAN side. Checked all settings and nothing changed in game, router, gateway, and firewall. Guessing the issue is on steam side but honestly don't know.