Can anyone explain why my code works on the Studio test run, but doesn't work on the real game?

I have a pretty big script here, and it took me forever to make it. Its 2 scripts split up by LocalScripts. I've tested it in Studio, and it works perfectly. Yet, when i play the actual game, it start making up problems. Here is the code now. Its 1 local script in StarterGui

local UIS = game:GetService('UserInputService')
local pressing
local Energy = 90
local player = game.Players.LocalPlayer
local character = player.Character
local PrettyColor = false
if not player or not character.Parent then
    character = player.CharacterAdded:wait()
end
local torso = character.LowerTorso
local fire = Instance.new("Fire")
fire.Parent = torso
fire.Enabled = false
fire.Heat = 6
fire.Size = 6


UIS.InputBegan:connect(function(inputObject, gameProcessedEvent)
    if not gameProcessedEvent then
        if inputObject.KeyCode == Enum.KeyCode.C then
            pressing = true
            while pressing do
                wait(.2)
                Energy = Energy + 1
                    fire.Enabled = true
                    if PrettyColor == false then
                    fire.Color = Color3.new(255,255,255)
                    fire.SecondaryColor = Color3.new(255,255,255)
                    PrettyColor = true
                    end
                    _G.GetEnergy(Energy)
            print('Charging....')

            end
        end
        fire.Enabled = false
    end
end)

UIS.InputEnded:connect(function(inputObject, gameProcessedEvent)
    if not gameProcessedEvent then
        if inputObject.KeyCode == Enum.KeyCode.C then
            pressing = false
            print('u stopped pressing :)')
            fire.Enabled = false
        end
    end
end)