why not open shop gui when touch part?

debounce = false

function onTouched(hit)
    local plr = game.Players:GetPlayerFromCharacter(hit.Parent)
    if plr and debounce == false then
        debounce = true
        
        plr:WaitForChild("PlayerGui").ShopGui.Frame.Visible = true
        debounce = false
    end
end

script.Parent.Touched:connect(onTouched)

how touch part open shop did not work

The script does not work because there is no shop gui in the PlayerGui for the server this can only be used via local script (or with a remote function)

local RemoteEvent = Instance.new("RemoteEvent")
RemoteEvent.Parent = game.Workspace
RemoteEvent.Name = "ShopEvent"

function onTouched(hit)
    local plr = game.Players:GetPlayerFromCharacter(hit.Parent)
    RemoteEvent:FireClient(plr)
end

script.Parent.Touched:Connect(onTouched)

this script is placed in the brick

game.Workspace:WaitForChild("ShopEvent")
local debounce = false

game.Workspace.ShopEvent.OnClientEvent:Connect(function ()
	if debounce == false then
		script.Parent.Frame.Visible = true
		debounce = true
	end
end)

this script is placed in a local script in the shop gui