what does unable to assign property meshid. Script write access is restricted mean?

Hi, I made a script were when you click E, a lightning bolt appears in front of your character. The lightning bolt is a meshpart, and just recently I added lookVector to it.

But when I tried to summon a lightning bolt this error appeared

18:38:26.923 - ContextActionService: Unexpected error while invoking callback: Unable to assign property MeshId. Script write access is restricted

Is there anyway for me to fix it?

Here is my script:

local player = game.Players.LocalPlayer
local character = player.CharacterAdded:Wait() 
local head = character:WaitForChild("Head")

local Humanoid = character:WaitForChild("Humanoid")
local torso = character.UpperTorso
local mouse = player:GetMouse()

local bodyparts = game.Players.LocalPlayer.Character:GetChildren()


local Workspace = game.Workspace





local God = player.PlayerGui.ChooseCharacter.God
--BREAKLINE--

local function onKeyPress(actionName, userInputState, inputObject)
    if userInputState == Enum.UserInputState.Begin then

    if inputObject.KeyCode.Name =="Z" then 
        if God.Value =="Zeus" then
            game:GetService("Chat"):Chat(player.Character.Head, "CHARIOT","Blue")
            print("Test Z")
        elseif God.Value =="Poseidon" then --SUMMON HORSE(POSEIDON)--
            game:GetService("Chat"):Chat(player.Character.Head, "CHARIOT","Blue")
        end
    end

    if inputObject.KeyCode.Name =="T" then  
        if God.Value =="Zeus" then
            game:GetService("Chat"):Chat(player.Character.Head, "MASTERBOLT!","Blue")
            local tool = game.Workspace.BetaBolt:Clone()
            character.Humanoid:EquipTool(tool)
            wait(5)
            tool:Destroy()
        elseif God.Value =="Poseidon" then --summon trident--
            game:GetService("Chat"):Chat(player.Character.Head, "TRIDENT!","Blue")

        end
    end



       if inputObject.KeyCode.Name =="F" then
        if God.Value =="Zeus" then
        game:GetService("Chat"):Chat(player.Character.Head, "FEEL THE POWER OF A TRUE GOD!","Blue")
        Humanoid.HipHeight = 20


        for _,body in pairs(bodyparts) do
    if body.Name == "RightHand" then 
        body.BrickColor = BrickColor.new("Dark blue") 
    end
        end


        local lightning = Instance.new("Part",Workspace)
        lightning.Shape = ("Cylinder")
        lightning.BrickColor = BrickColor.new("Institutional white")
        lightning.Transparency = 0.5
        lightning.CanCollide = false
        lightning.Size = Vector3.new(2, 9, 5)


        wait(6)
        --end of power--

        Humanoid.HipHeight = 1.35
        end
    end


    if inputObject.KeyCode.Name =="Q" then 
        if God.Value == "Zeus" then
            game:GetService("Chat"):Chat(player.Character.Head, "LIGHTNING DASH!","Blue")
            head.CFrame = head.CFrame * CFrame.new(0,0,-50)
        else
            print("FAIL LIGHTNING DASH")

        end
    end


         --THIS IS THE THUNDERBOLT PART WERE I NEED HELP--

    if inputObject.KeyCode.Name =="E" then 
         if God.Value == "Zeus" then  
            game:GetService("Chat"):Chat(player.Character.Head, "THUNDER!","Blue")
            local damage = game.Workspace.Damage:Clone()
            local Thunder = Instance.new("Part")
            Thunder.Name = ("ThunderBolt")
            local mesh = Instance.new("MeshPart",Thunder)
            mesh.MeshId = "rbxassetid://978945957"
            mesh.TextureId = "rbxassetid://978945981"
            Thunder.Anchored = true


            mesh.CFrame.lookVector = character.CFrame.lookVector
            mesh.Scale = Vector3.new(5,20,15)


            damage.Position = Vector3.new(mouse.hit.x,mouse.hit.y,mouse.hit.z)
            damage.Parent = workspace
            Thunder.Position = Vector3.new(mouse.hit.x,mouse.hit.y,mouse.hit.z)
            Thunder.Parent = workspace
            wait(1)
            damage:Destroy()
            Thunder:Destroy()



        end


    if inputObject.KeyCode.name =="Z" then
        if God.Value =="Zeus" then
        game:GetService("Chat"):Chat(player.Character.Head, "EAGLE FLIGHT!","Blue")
               else

        end
    end




        end
    end
end

game:GetService("ContextActionService"):BindAction(
    "keyPress", 
    onKeyPress, 
    false, 
    Enum.KeyCode.Q,
    Enum.KeyCode.E,
    Enum.KeyCode.F,
    Enum.KeyCode.T,
    Enum.KeyCode.Z
)