Is this in character creation, or after that?
Have you tried joining different games?
Did you try different ways to connect? The lobby or friend invite are available if you are both playing the same version, Steam or GOG, and Direct Connection should work in any case.
Have you tried hosting?
If you lower the game resolution and switch to windowed display mode, does that make a difference, or at least let you see if there are any pop-up windows in the background from an anti-virus or firewall program, etc?
Are you shutting down all non-essential programs before starting the game, especially anti-virus and anything network related?
Try each 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 check the Event Viewer, does that give an error code or 'Faulting Module' file name that might help identify the cause of the crash?
- click Start (or WinKey-R), then type "event viewer" into the search box. in Windows 10, 'event' should bring up 'View event logs'.
- after starting the Event Viewer, expand 'Windows Logs' in the left column and select 'Application'
- in the center column, look for a recent error (maybe sort by Date and Time) for the game
- check the information under the 'General' tab below the list of events, starting with "Faulting application name..."
