The current pre-release of the client ("pioneer" in the version) is only compatible to itself. So you can only play with other testers. Please be aware!
For further explanation: the game doesn't have a concept of mod versions. This ever new version needs to have a different uid, otherwise it could not pick an old mod version for replays while keeping the new version for playing.
win + r C:\ProgramData\FAForever\bin\ForgedAlliance.exe hit enter
or go to that directory and make a shortcut. If you wana play campaign offline modify the shortcut to add /init init_coop.lua behind the target to the shortcut
