Why cant I weld Mesh parts?

local players = game.Players.LocalPlayer
local torso = game.Players.LocalPlayer.Character:FindFirstChild("RightArm") or game.Players.LocalPlayer.Character:WaitForChild("RightArm")
local coat = script.Parent

local weld = Instance.new("Weld")
weld.Parent = script.Parent
weld.Part0 = coat
weld.C0 = coat.CFrame:inverse()
weld.Part1 = torso
weld.C1 = torso.CFrame:inverse()
coat.Anchored = false

coat.CFrame = torso.CFrame * CFrame.new(0,0,0)

Been trying for hours but it just wont work.

#Edit

local players = game.Players.LocalPlayer
local character = players.Character
local Torso = character:FindFirstChild("UpperTorso") or character:WaitForChild("UpperTorso")
local Coat = script.Parent.Parent.CoatMesh

Coat.CFrame = Torso.CFrame * CFrame.new(0,-1.5,1)
local weld = Instance.new("Weld")
weld.Parent = script.Parent
weld.Part0 = Coat
weld.C0 = Coat.CFrame:inverse()
weld.Part1 = Torso
weld.C1 = Torso.CFrame:inverse()
Coat.Anchored = false

This works when its inside a Tool, but I want it welded to my torso at all times without a tool. Here's how it looks currently https://imgur.com/a/pKAvclt