Are you shutting down all non-essential programs before starting the game, especially anti-virus and anything network related (utility or monitoring programs, etc)?
Have you checked your firewall settings? Many routers have built in firewalls, which could block inbound connections from the game.

Have you tried switching who was hosting?

Have you tried joining anyone else?

Have you tried hosting/joining an Arena match?

Try going into Arena mode, create an arena, open the Connectivity menu and check the settings, then exit to the main menu and try joining. Alternately, create a multiplayer game lobby, exit and try joining.

If you are using any mods, try testing in a new profile without any mods enabled.

Try verifying local files: in the Steam library, right click on the game and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
With the GOG version, in the (optional) Galaxy client, select Divinity: Original Sin 2 in the left column, then click on the More button, and in the Manage menu select 'Verify / Repair'.

If you use Discord, joining by Discord invites may be an option.

Try resetting your network adapters:
- click Start (or Search in Win 10), type cmd into the search box, right click Command Prompt and select run as administrator.
- type the following command and hit Enter
netsh winsock reset
- when that is done, there should be a message 'Winsock reset completed successfully'
- type exit and hit Enter, then reboot your computer.
For more details, see:
[url=https://iihelp.iinet.net.au/Resetting_Network_Adapter_(Winsock_Reset]https://iihelp.iinet.net.au/Resetting_Network_Adapter_(Winsock_Reset[/url])

If you can not join other people, either, try starting the game, switch to windowed mode and lower the game resolution (and maybe check the option to mute the sound volume when the game doesn't have focus), start a multiplayer game, hit Esc, open the Connectivity Menu, optionally disable online multiplayer (if it is enabled) and make sure LAN Connections is enabled (or that can be done in the options before starting a new game).
Next, start the game again from the 'EoCApp.exe' program file (doesn't matter if the first instance is started through Steam/Galaxy or the executable), select Join Online Game in the Campaign section, switch to the LAN tab, rather than Online, and try joining.

Have you tried joining any other GOG player using Direct Connection, or has your friend tied joining any other Steam players?


Please email supportdos2@larian.com with a link to this topic and a dxdiag report, for both systems (WinKey-R, type in dxdiag and hit enter, then when it finishes loading click on the 'Save All Information...' button and save the report somewhere handy).
Also check the '..\Divinity Original Sin 2\DefEd\bin' folder for the gold.log and network.log files.
Rename the current network.log file, try hosting a game and get the other person to try joining, exit the game and rename the new network.log file, then swap who is hosting and repeat the same test, then include all of the network.log files for both systems in the email.