How to make a custom health GUI?

I tried this but it doesn't work, only works in solo mode in studio. I tried it online, it gives me no errors either. And it's in a local script in the Starterpack

local player = script.Parent.Parent.Parent.Parent.Parent.Parent
local char = player.Character
while true do
    local humanoid = char:FindFirstChild("Humanoid")
    if humanoid ~= nil then
        local bar = script.Parent
        bar.Size = UDim2.new(- humanoid.Health*-0.006, 0, 0.2, 0)  ---Multiplyed it by .006 since total length is .6 and the player has 100 health points.
    end
    wait()
end