Because there is not version 125548 for Linux. 1) 1.63.126652 - http://forums.bistudio.com/showthread.php?181699-ARMA-2-Operation-Arrowhead-Linux-Server-beta-1-63-126652 2) and nonsteam 1.63.112555 - http://forums.bistudio.com/showthread.php?168768-ARMA-2-Operation-Arrowhead-Linux-Server-beta-1-63-112555