canehdian

Hello everyone, So I just downloaded Arma 2, Arma 2: Operation arrowhead and Arma 2: DayZ mod. Whenever I tried to join a server I get this message saying that certain files are not signed by a key accepted by this erver. Here is a picture. I have tried deleting all listed files, checking the game integrity of arma 2, arrowhead and dayz and even re downloading them all. Can anyone please give me some help on this one?