My health bar script works in studio testing, but not in the actual game?

I'm trying to make a game and I made a health bar. I've maid health bars before and normally this isn't a problem. I tested it in studio and it worked just like intended, but when I tested it in the actual game on roblox, it didn't work. Script:

local healthgui = script.Parent
local frame = healthgui:WaitForChild("Frame")
local number = healthgui:WaitForChild("Number")
local player = game.Players.LocalPlayer
local char = player.Character
local healthstat = player:WaitForChild("Health")
local maxstat = player:WaitForChild("MaxHealth")
local words = healthgui:WaitForChild("Health")

local green = Color3.new(0,255,0)
local red = Color3.new(255,0,0)
local yellow = Color3.new(255,255,0)

char.Humanoid.Changed:connect(function()
    local health = char:WaitForChild("Humanoid").Health
    local maxhealth = char:WaitForChild("Humanoid").MaxHealth
    local redzone = maxhealth*0.25
    local yellowzone = maxhealth*0.5
    if health <= redzone then
        frame.BackgroundColor3 = red
        number.TextStrokeColor3 = red
        words.TextStrokeColor3 = red
    elseif health <= yellowzone then
        frame.BackgroundColor3 = yellow
        number.TextStrokeColor3 = yellow
        words.TextStrokeColor3 = yellow
    else
        frame.BackgroundColor3 = green
        number.TextStrokeColor3 = green
        words.TextStrokeColor3 = green
    end
    frame:TweenSize(UDim2.new(healthstat.Value/maxstat.Value*0.93,0,0,24),"Out","Quart",1)
    number.Text = healthstat.Value.."/"..maxstat.Value
end)

while wait() do
    local level = player:WaitForChild("leaderstats"):WaitForChild("Level")
    if player.Name == "Blue_Deku19" then
        char:WaitForChild("Humanoid").MaxHealth = (level.Value * 5 + 95)*5
        healthstat.Value = char.Humanoid.Health/5
        maxstat.Value = char.Humanoid.MaxHealth/5
    else
        char:WaitForChild("Humanoid").MaxHealth = level.Value * 5 + 95
        healthstat.Value = char.Humanoid.Health
        maxstat.Value = char.Humanoid.MaxHealth
    end
end

I tested which part it fails at by making it make a part wherever your current player is and I moved that around, it didn't even make the variables in the first part. This is a local script in StarterGui, does anyone know what's wrong with it? Sorry if it's long e.e. Also, it showed no problems whatsoever in the output when I was testing it in studio.