I have a fresh install of LaunchBox on my NVIDIA Shield and went to download RetroArch and it keeps saying failed to download. I downloaded dolphin just fine.
I've deleted the RetroArch files in the emulator folder as well. When I look at "Manage RetroArch" it says RetroArch is not installed Latest Version: Unknown
I'm using Version 1.18-beta-5 of Launchbox and had no issues installing on my other NVIDIA shield.