Instead of launching the HC from a Steam installation, use SteamCMD to download a of Arma 3, then treat the HC as a second server instance with -client mode.
: Use Task Manager to completely end the Steam.exe process and restart it. arma 3 headless client steam authentication failed hot
: Authentication issues often occur when trying to connect an HC to a "Live Hosted" (non-dedicated) server. Using a Dedicated Server setup is highly recommended for HC stability. Troubleshooting Steps Instead of launching the HC from a Steam