Well, as I'm stuck temporarily on an XP machine and Commander is my only option, I haven't been able to get into the server until recently. A lot of people aren't able to get other launcher programs to work as well. The following seems to solve the issue for me and maybe it will work for you.
1. Open Commander
2. Open the settings menu on the bar at top right.
3. In the space where it says "Additional Launch Parameters" delete anything there, then copy and paste the following:
-mod=@DayZ_Epoch
4.Close the settings menu and click on the server to launch the game.
It appears that Commander isn't reporting the server configs to the game when it launches when you try to join. This pre-loads the parameters in manually.
Hope this helps,
Sand
