UpdateDatastore always show failed to lock?

Hi! I'm working on a cross-server serverlock. I started by using a datastore. It will be updated when someone with rank 14 or higher says ;slock, then the datastore would get updated... This is what I currently have:

local DataStoreService = game:GetService("DataStoreService")
local LockStore = DataStoreService:GetDataStore("ServerLock")

game.Players.PlayerAdded:connect(function(player)
    player.Chatted:connect(function(msg)
        if player:GetRankInGroup(3809918) >= 14 then

            if msg == ";slock" then
                print("slock cmd")
                local success = pcall(function()
                    return LockStore:UpdateAsync("Lock", true)                  
                end)
                if success then
                    local msg = Instance.new("Hint")
                    msg.Text = "Servers locked"
                    msg.Parent = workspace
                else
                    local msg = Instance.new("Hint")
                    msg.Text = "Failed to lock servers"
                    msg.Parent = workspace
                end
            end
        end
    end)
end)

I already created the datastore. It always says "Failed to lock servers" on the top... What am I doing wrong? There is no output. Thanks for your help, Jonas