Localscript does not work, The blocks do not show letters ?

I create a event Players will pick up the gift box and receive the letters. I created the blocks in the workspace and put in that surfacegui. The blocks will display the letters they already own I created a localscript and put it in startergui but it didn't work This is my script

local d = script.Parent.Parent.event.D
local o = script.Parent.Parent.event.O

function checkd()
    if d.Value == true then
        game.Workspace.D.SurfaceGui.Enabled = true
    end
end
function checko()
    if d.Value == true then
        game.Workspace.O.SurfaceGui.Enabled = true
    end
end

d.Changed:Connect(checkd)
o.Changed:Connect(checko)