why isnt it in sandbox anymore?

my server has no gamemode. no HUD no weapons no spawnmenu. nothing.

how can i set it back to sandbox?

bottom right of main menu, or when you’re setting up a game you can set it in the settings?

That would be if he was playing in Single Player or Hosting a server from his computer, but I’m assuming that he has a dedicated server, I don’t know much about hosting, but I think you have to go into your VPS or control panel and change it back there.

make sure that you have defined “+gamemode [gamemode]” correctly in the .bat file you use to launch the server, if you do use such a file

Maybe his dedi has some files missing