How to make a game where you are always in First Person Mode?

I have made a script that lets you see in first person when you play solo. However it doesn't work when you start a server or play the actual game. Can anybody help?

This is the code I used:

game.Players.PlayerAdded:connect(function(player)
while true do   
    player.CameraMode = Enum.CameraMode.LockFirstPerson
    wait()
    end
end)