On / Off Mute Button Values Not Changing?

Hi folks, I know I've already asked about 100 questions (Kidding, but it feels like it) but as a novice I still pick up new things and new errors along the way. Cutting to the chase, I have this code for my game in which I would like people to have the option to turn music on or off in game, but when I click the button it doesn't want to work. Please take a look at what I've tried.

script.Parent.MouseButton1Down:Connect(function()
	IsOn = true
	if IsOn == true then
		for i,v in pairs (script.Parent.Parent.TextButton:GetChildren())do
			if (v.ClassName == "Sound") then
				v.Volume = 1
				script.Parent.Image = "rbxassetid://205571713"
			elseif IsOn == not false then
				IsOn = false
			end
		end
		end
			script.Parent.MouseButton1Down:Connect(function()
			IsOn = false
			if IsOn == false then
			for i,v in pairs (script.Parent.Parent.TextButton:GetChildren())do
			if (v.ClassName == "Sound") then
				v.Volume = 0
				script.Parent.Image = "rbxassetid://205571728"
			elseif IsOn == not true then
				IsOn = true
			end
			end
		end
	end)
end)

Any help would be very much appreciated, thank you all so kindly for your time and effort. I hope to hear from you soon!