Why does this plugin script only work in command bar?

I've been trying to get this plugin script to work for a-while now, it worked at some point but then suddenly stopped working, it won't create the toolbar or anything. I went back to basic's to test and see if it work's and it still didn't work. But the exact same script work's in the command bar, can anyone tell me why?

Any help appreciated.

The basic script I tried:

-- Variables
local Plugin = PluginManager():CreatePlugin()
local Toolbar = Plugin:CreateToolbar("Test plugin bar")
local Button = Toolbar:CreateButton("Test plugin","No description","http://www.roblox.com/asset/?id=78930759")

-- Main Script
Button.Click:connect(function()
    local h = Instance.new("Hint",game.Workspace)
    h.Text = "Test worked."
    wait(2)
    h:Destroy()
end)