This works when I test it in studio but not in an actual server?

Okay, so I made this script which is supposed to make the player run

It works perfectly in a Studio test but doesn't work at all once I'm in an actual server, please help!

Here is my code:

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()

local character = player.Character

if not character or character.Parent == nil then
    character = player.CharacterAdded:wait()
end
local sprint = Instance.new("BoolValue",character)
sprint.Name = "sprint"

local humanoid = character.Humanoid
humanoid.WalkSpeed = 10

local debounce = false

mouse.KeyDown:connect(function(key)
    if key:byte() == 48 and debounce == false then
        humanoid.WalkSpeed = 20
        debounce = true
        for i=1,20 do
            wait()
            game.Workspace.Camera.FieldOfView = game.Workspace.Camera.FieldOfView + 1
        end
    end 
end)

mouse.KeyUp:connect(function(key2)
    if key2:byte() == 48 and debounce == true then
        debounce = false
        humanoid.WalkSpeed = 10
        for i=1,20 do
            wait()
            game.Workspace.Camera.FieldOfView = game.Workspace.Camera.FieldOfView - 1
        end
    end
end)

I would really appreciate it if you could help me out, thanks!