User thumbnail never loading.. what should I do?

I have this script for when a player joins the game, all you have to worry about is "PFP" I set its image value to the users thumbnail so it is preloaded for when a player wins an arena battle. Even with this, the users thumbnail in studio test mode is still the icon that shows no image is in the imagelabel, no errors

game.Players.PlayerAdded:Connect(function(plr)
	local fold = Instance.new("Folder",plr)
	fold.Name = "Stats"
	local battle = Instance.new("BoolValue",fold)
	battle.Name = "battle"
	battle.Value = false
	local kills = Instance.new("IntValue",fold)
	kills.Name = "kills"
	kills.Value = 0
	local pfp = Instance.new("ImageLabel",fold)
	pfp.Name = "PFP"
	local content, isReady = game.Players:GetUserThumbnailAsync(plr.UserId, Enum.ThumbnailType.HeadShot, Enum.ThumbnailSize.Size352x352)
	pfp.Image = content
end)

Players in the test server are generated as you start the server, therefore I believe that you can't actually load their thumbnails, it works when I tested it in the real game though.