I have a friend with the exact same issue .. was working fine yesterday. Now it's doing this. Only thing I can think of is he installed the a3 launcher and started downloading lots of mods so he could play exile.... we restarted computer. Uninstalled arma 3. Reinstalled still missing a file. Uninstalled steam and everything that went with it mods and all.. reinstalled still same issue no mods nothing . Missing 1 file. I'm at work atm.. I'm going to see what I can do when I get home.. I was gunna wipe his comp but he doesnt has a genuine copy of Windows to reinstall from.. HELP SOMEONE