He couldn't click any buttons in the multiplayer lobby, so he couldn't host a game or join one. Only thing of note is that he went straight to the beta after downloading Buckshot Roulette for the first time. We tried:
- File Integrity Reset
- Uninstall/Reinstall
- Playing the singleplayer first before doing multiplayer
- Beating the singleplayer in the non-beta version of the game, then trying again
- Clicking without full screen active (in windowed mode)
Provided is his player log.