How am I adding one string to another wrong? (question updated to be more detailed)

This is for a password thingy. I have a part with a surface gui that is supposed to display the password once entered. I also have a string value in the button(s) which once pressed should add the string value to the surface gui's textbox's text while still including previous text. It does nothing. The important part is lines 18 - 20 because those parts are the parts not working.

Full script:

U = script.Parent.CodeKey.SurfaceGui.TextBox.Value

for i, v in pairs(script.Parent:GetChildren()) do
	if v:FindFirstChild('ClickDetector') then	
		v.ClickDetector.MouseClick:connect(function()
			v.Ok.Value = v.Ok.Value+1
			if v.ClassName == "Part" and v.Name == "Button" then
				print(v.Ok.Value)
				if v.Ok.Value == 1 then
					v.Ok.Value = v.Ok.Value-1
					v.Size = v.Size-Vector3.new(0, 0, .2)
					v.Position = v.Position-Vector3.new(0, 0, .1)
					wait(.03)
					v.BrickColor = BrickColor.new(1022)
					wait(.05)
					v.Size = v.Size+Vector3.new(0, 0, .2)
					v.Position = v.Position+Vector3.new(0, 0, .1)
					if v:FindFirstChild('value') then
						script.Parent.CodeKey.SurfaceGui.TextBox.Text = script.Parent.CodeKey.SurfaceGui.TextBox.Text .. v.Value.Value 
						print(script.Parent.CodeKey.SurfaceGui.TextBox.Text)
					end
					wait(.02)
					if v.Typ.Value == 1 then
						v.BrickColor = BrickColor.new(194)
					end
					if v.Typ.Value == 2 then
						v.BrickColor = BrickColor.new(327)
					end
					if v.Typ.Value == 3 then
						v.BrickColor = BrickColor.new(310)
					end
				end		
			end
		end)
	end
end

part that doesn't work:

if v:FindFirstChild('value') then
						script.Parent.CodeKey.SurfaceGui.TextBox.Text = script.Parent.CodeKey.SurfaceGui.TextBox.Text .. v.Value.Value 
						print(script.Parent.CodeKey.SurfaceGui.TextBox.Text)
					end