Vault21

I'm joining through the game on multiplayer server. I purchased it from steam and whenever I try to join I get that long error message. I tried to disable the expansions to play Day Z. The error I got to disable expansions to play is not letting me disable them. I do get that message, I just don't know how to fix it. any solutions?

I just bought the entire Arma 2 bundle with all the arma games, including Day Z Mod with all the expansions yesterday. I've been having some trouble joining some servers, I'm currently up-to-date with the 1.63 version, but when I join any Day Z server it loads for a few seconds then it shows the server greeting and joining in, then it acts like it's going to play. But then I get kicked and a long error message shows saying something like "C:Program Files of the location of the game directory, then below it says, "are not signed by a key accepted by this server. To play on this server, remove listed files or install additional accepted keys." Then on the side of the listed servers, there are red circles and orange circles with question marks in them. All the servers I have tried do the same problem I described. I am lost, does anyone know how to fix this? Here are some images of the problem.