Here is a quick fix for everyone who is having issues connecting to a game session. After doing the following start your game and pick campaign.
Guide to Fix Lost Connect to Game Server / Kicked To Lobby
Open Windows explorer and then Program Files x86. Look for Easy Anti Cheat folder and right click on it and select copy.
Now go here:
- C:Program Files (x86)SteamSteamAppscommonBack4BloodBetaEasyAntiCheat
Right click in the folder and paste the EAC into it.
Delete the EasyAntiCheat_EOS_Setup.exe file and close Windows Explorer. Start game up.