Why wont my talk script work?

It's playerGui not starterGui. Also, you are supposed to put these in a screen GUI. new structure:

-- PlayerGui
----ScreenGui
------Button
--------LocalScript(Below)
------TextBox
--------TextLabel

local sp = script.Parent

button = sp
player = game.Players.LocalPlayer

msg = player.PlayerGui.ScreenGui.TextBox.TextLabel

msg.Visible=false

function Talk()
        player.Character.Torso.Anchored=false
        msg.Visible=true
        wait(3)
        msg.Text="Logan: Nice to see you again."
        wait(3)
        msg.Text="Mr.Clark: We have bad news."
        wait(2)
        msg.Text="Mr.Clark: Even though you just came out of the military..."
        wait(5)
        msg.Text="Mr.Clark: You are joining back."
        wait(3)
        msg.Text="Logan: Bu-but, why?"
        wait(3)
        msg.Text="Mr.Clark: A year ago, Captain.Mackintosh was kidnapped by the enemies."
        wait(4)
        msg.Text="Mr.Clark: We just found out now currently in 2014"
        wait(3)
        msg.Text="Logan: Oh s***!!, is he alright!?!"
        wait(3.1)
        msg.Text="Mr.Clark: We are not sure"
        wait(4)
        msg.Visible=false
    end

sp.MouseButton1Click:connect(function(button)
            Talk()
end)

I've Tested it Again