After being told by your Twitter the update was live and the servers were holding up I decided to check for myself, No Update... Turned on DayZ, No Servers. I restart the game, Nothing. Restart my xbox. Nothing. Uninstall DayZ, Reinstall, Hard restart finally yields two servers. However, upon clicking on the non password protected one, I get booted back to server selection.
This has been the case since your Xbox Insider launch and it doesn't seem like it will be resolved by your Game Preview launch.