Six Launcher has begun updating Arma clients to the latest beta patch version 95054. The two games.on.net Day Z servers have also been updated to the same version.
There's a bug with this beta where Battleye won't initiate and you'll get kicked from the server. You need to manually download the new Battleye client .DLL
and overwrite the existing .DLL file in the ../Expansion/BattlEye folder in your Operation Arrowhead folder.
You'll then be able to join servers successfully.