I seem to be experiencing the same issues. I usually launch my game from DZSA launcher but i could not find the server on there. I went on steam and loaded all the right mods and put the parameters for the server in and got hit with this message. I've reinstalled dayz and restarted my computer aswell.
EDIT: I uninstalled and unsubscribed from everything, i then had to validate the mods when i reinstalled because of the error below
Hi guys my name is Terriors and I recently got white listed. I come from playing mostly darkrp on Gmod but I've been looking for something more realistic and authentic. I go by the name Clive Bannister in game, I already spent a few hours on the server and am loving it. I hope to see more of you guys there.