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!
open the file "Game.prefs". mostly located in:
C:\Users\YOURNAME\AppData\Local\Gas Powered Games\Supreme Commander Forged Alliance\Game.prefs
open the file and search for "ui_scale"
change the line so it looks like:
ui_scale = 1,
save it; start the game.
