In my game, every button won't even function as a normal button?

I'm making a GUI for someones game (Start GUI) but EVERY button in the game won't change color when a mouse hovers, and the mouse doesn't turn black. (Like any normal button) It's pretty much like the button is a TextLabel (I used a button, not text label!) Please help, here's the script for one of the buttons I think is causing the problem.

local player = script.Parent.Parent
local gui = script.Parent
local sound = Instance.new("Sound",gui)
sound.SoundId = "http://www.roblox.com/asset/?id=221235033"
sound.Pitch = 1
sound.Volume = 0.7
local frame = gui.Frame
Play = script.Parent.Frame.Play
sound:play()

function OpenCloseGui()
    gui:remove()
end

Play.MouseButton1Down:connect(OpenCloseGui)

Thanks! -club101coolguy