Filtering Enabled Welding script is not working in game but in studio?

Problem

My script is, when the player joins it gets a part inside the workspace and welds it into the player. This works in studio but not in game. I've used FireClient so send code to Server to client but it doesn't work. What am I doing wrong?

LocalScript:

local Players = game:GetService('Players')
local Player = Players.LocalPlayer  
local char = Player.Character
local LeftArm = char.Torso

game.ReplicatedStorage.DoDun.OnClientEvent:Connect(function(Part)--Get the RemoteEvent
    print("hoolio")
     Part.CFrame = LeftArm.CFrame * CFrame.new(-5,0,0)
local weld = Instance.new("Weld")--Welds it to left arm -5 on the x scale
weld.Part0 = LeftArm
weld.C0 = LeftArm.CFrame:inverse()
weld.Part1 = Part
weld.C1 = Part.CFrame:inverse()
weld.Parent = Part
print("ok")
Part.Anchored = false
Part.CanCollide = false
print("non")
end)

Server Script

game.Players.PlayerAdded:Connect(function(Player)--Get the player when joines
        local Part = game.ReplicatedStorage.Part:Clone()--Clones the part 
        Part.Parent = workspace
   game.ReplicatedStorage.DoDun:FireClient(Player, Part)--FireClient with the RemoteEvent 
end)