Waiting for the player to click a button, why am I getting an error?

The game is supposed to wait until a player clicks the "Continue" button, although this doesn't work at all. It instead does nothing and the output gives, "DialogueBox is not a valid member of PlayerGui" which when the dialogue box exists within the StarterGui. (Line 26 of the localScript) Here is the entire script, it's long, and I may have things in the wrong place.

local Controller = require(game.Players.LocalPlayer:WaitForChild("PlayerScripts"):WaitForChild("PlayerModule")):GetControls()
local triggered = false -- Debounce
local UIS = game:GetService("UserInputService") -- Disable Movement

game.ReplicatedStorage.AddyyNPC.OnClientEvent:Connect(function() -- Run on touch
	if triggered == true then
		return nil
	end
	if triggered == false then
		triggered = true
		Controller:Disable()
		game.Workspace.RealAddyy.Head.Interact.Enabled = false
		game.Workspace["Addyy Music"].AddyysMusic.Volume = 0.2
		script.Parent.Parent.DialogueBox.Enabled = true
		workspace.CurrentCamera.CFrame = workspace.CAMS.Dialouge.Addyy.CFrame
		script.Parent.Parent.DialogueBox.NPCName.TextLabel.Text = "???"
		script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "."
		wait(1)
		script.Parent.Parent.DialogueBox.Main.TextLabel.Text = ".."
		wait(1)
		script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "..."
		script.Parent.Parent.DialogueBox.Continue.Visible = true
	end
end)

script.Parent.Parent.DialogueBox.Continue.MouseButton1Click:Connect(function()
	script.Parent.Parent.DialogueBox.Continue.Visible = false
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "..."
	script.Parent.Parent.DialogueBox.C1.Text = "Who are you?"
	script.Parent.Parent.DialogueBox.C2.Text = "Hello?"
	script.Parent.Parent.DialogueBox.C1.Visible = true
	script.Parent.Parent.DialogueBox.C2.Visible = true
end)

script.Parent.Parent.DialogueBox.C1.MouseButton1Click:Connect(function() -- Choice 1
	script.Parent.Parent.DialogueBox.C1.Visible = false
	script.Parent.Parent.DialogueBox.C2.Visible = false
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "W"
	wait(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Wh"
	wait(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who-"
	script(2)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- O"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh w"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh wh"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh who"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh who a"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh who ar"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh who are"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh who are y"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh who are yo"
	script(0.5)
	script.Parent.Parent.DialogueBox.Main.TextLabel.Text = "Who- Oh who are you?"
end)

script.Parent.Parent.DialogueBox.C2.MouseButton1Click:Connect(function() -- Choice 2
	script.Parent.Parent.DialogueBox.C1.Visible = false
	script.Parent.Parent.DialogueBox.C2.Visible = false
end)