What is wrong with this mute/unmute script?

function OnClick()
local UnMuted =script.Parent.Parent.UnMuted 
local Muted =script.Parent.Parent.Muted



if script.Parent.Parent.ImageButton.Image == UnMuted then
	
	script.Parent.Parent.FireSound:Stop()
	
	
	script.Parent.Parent.ImageButton.Image = Muted
	
elseif script.Parent.Parent.ImageButton.Image == Muted then
	script.Parent.Parent.FireSound:Play()
	
	script.Parent.Parent.ImageButton.Image = UnMuted
	
	
	end
	
	
end


script.Parent.MouseButton1Click:connect(OnClick)

Where the Items are located -->http://prntscr.com/9rpzxt

Anyone know what the problem is? :c

Problem: The Images Won't change and the sound won't stop!

PS: The Mute and Unmute buttons are string vallues with the texture id's