Why is my RemoteEvent erroring? Cannot pass value onto object?

I'm trying to make a script that will make a Gui pop up on your screen when you pick up an item, and when I fire the event to make the gui script work, it tells me "value cannot be passed to object" Here's my script:

local toolname = "Test"
local tool = game.ServerStorage:FindFirstChild(toolname)

script.Parent.MouseClick:Connect(function(click)
    tool.Parent = click.Backpack
    click.PlayerGui.EventText.PickUpEvent:FireClient(toolname, 0.02)
end)

The item goes into my backpack, but the event errors.