Why won't this script work? (I need assistance ASAP)

local part = script.Parent
local player = game.Players.LocalPlayer

if player.PlayerGui:FindFirstChild(“NPCmessage”) then
part:FindFirstChild(“ClickDetector”):Destroy()
else
local ClickDetector = Instance.new(“ClickDetector”)
ClickDetector.Parent = part

ClickDetector.MouseClick:Connect(function()
local GUI = script.NPCmessage:Clone
GUI.Parent = Player.PlayerGui
end)
end

in line 2 it was player then in line 12 it became Player with a capital

so just change Player to player in line 12

First of all, you made a spelling mistake with Clone(). After that, you accidentally set player to Player. Also PlayerGui may not have loaded yet so use WaitForChild to be on the safe side. Be a little careful next time!

local part = script.Parent
local player = game.Players.LocalPlayer -- Variable for player
local PlayerGui = player:WaitForChild("PlayerGui")

if PlayerGui:FindFirstChild(“NPCmessage”) then
part:FindFirstChild(“ClickDetector”):Destroy()
else
local ClickDetector = Instance.new(“ClickDetector”)
ClickDetector.Parent = part

ClickDetector.MouseClick:Connect(function()
local GUI = script.NPCmessage:Clone()
GUI.Parent = PlayerGui  -- Set's the GUI 
end)
end