Text button not working correctly. Help please?

Edit: As someone said, this LocalScript has no access to the ServerStorage, so use RemoteEvents instead.

That's because the parameters of MouseButton1Down are the x and y position of the mouse, not the player who clicked it. Just use: game.Players.LocalPlayer, assuming this is in a LocalScript, as all scripts in GUIs should be LocalScripts because the player that clicks it will always be the player who has the Gui.

Make a RemoteEvent inside the ReplicatedStorage named "CreateMessage"

And put these scripts in your game:

Script

function onClicked(player,message)
	local box = game.ServerStorage.HeadMessage:Clone()
	box.Parent = player.Character.Head
	box.Text = message
	box.Name = 'Newmessage'
	messagesto.BackgroundColor3 = Color3.new(90, 7, 255)
	wait(5)
	player.Character.Newmessage:Destroy()
end

game:GetService("ReplicatedStorage"):WaitForChild("CreateMessage").OnServerEvent:Connect(onClicked)

LocalScript

messagesto = script.Parent.Parent
local player = game.Players.LocalPlayer
function onClicked()
	game:GetService("ReplicatedStorage"):WaitForChild("CreateMessage"):FireServer(messagesto.TextBox.Text)
end



script.Parent.MouseButton1Down:Connect(onClicked)

That's all. :)

Original answer: (Wouldn't work online)

messagesto = script.Parent.Parent
local player = game.Players.LocalPlayer
function onClicked()
	local box = game.ServerStorage.HeadMessage:Clone()
	box.Parent = player.Character.Head
	box.Text = messagesto.TextBox.Text
	box.Name = 'Newmessage'
	messagesto.BackgroundColor3 = Color3.new(90, 7, 255)
	wait(5)
	player.Character.Newmessage:Destroy()
end

script.Parent.MouseButton1Down:connect(onClicked)