Why isnt the humanoid changing not working ?

it worked before

wait(0)
game.Players.PlayerAdded:connect(function(PlayersName)
game.Workspace:WaitForChild(tostring(PlayersName)):WaitForChild("Humanoid").Name = "NHumanoid"
end)

Try this:

game.Players.PlayerAdded:connect(function(player)
	repeat wait() until player.Character
player.Character.Humanoid.Name = "NHumanoid"
end)

You would wan to use the CharacterAdded event which includes the players character model.

This is an example only:-

game.Players.PlayerAdded:connect(function(plr)
	plr.CharacterAdded:connect(function(character)
		local hum = character:WaitForChild("Humanoid")
		hum .Name = "NHumanoid"
	end)
end)

Hope this helps.