Can't join a game or create a game

[Mouss400]

Hello, I am contacting you because my friend can't join my game and can't launch a game himself recently. He has uninstalled and reinstalled the game but nothing works, so I am forced to ask you for help. I am attaching a screenshot of what is displayed on my friend's screen when he tries to join a game or when he creates a game.
Sincerely  

[Beelzybub]

2 hours ago, Mouss400 said:

I am forced to ask you for help.

Have your friend use the Launcher/Tools/Clean game data menu and select all the boxes except "savegames". The select "Clean".

After that, don't start the game. While still in the launcher/tools menu, select "Open Game folder", then in the directory that opens.

delete the Mods folder if it exists. Close the launcher and verify files through Steam, then try again.