I played the game for 2 or 3 hours then all of a sudden got an appid error. If I ignored the error I could load into the game but then get a back end error(cannot login). So I did a reinstall, Now When I hit play on the launcher nothing happens, the game is running but I get no icon on my taskbar. If I launch the game from the game folder bypassing the launcher I get to the same point where it says back end error. I have tried deleting the /user/username/roaming/appdata folder for fatshark with no success.
Please see if anything here can help: https://support.fatshark.se/hc/en-us/articles/7709665369501--PC-How-to-Resolve-Darktide-Launcher-Issues