So even 2 years later i expirienced this problem. What solved it for me on playerside (joining a server) was:
1. Reinstalling the mod on the latest version ( or the version of the server) into the "Mods" folder in the arma 3 dictonary. I did not copy the exile folder in the root folder of arma 3 only in the said mods folder ( create one if there isnt one).
2. Download the exile server files at the download section of this website and open the keys folder in it, there should be a file called exile.bikey in it. Copy exile.bikey into the Keys folder of your arma 3 dictonary.
maybe this will help if people still experience problems with this.