How do I keep track of the player when I teleport him/her? (HTTP 500 User if Offline)

I'm trying to match a group of players together and put them together in one place. However, when I try to receive information of the player joining the game, I receive this error: HTTP 500 (HTTP/1.1 500 User is offline)

I've used a bit from the Matchmaking tutorial on the roblox wiki in order to make this code and I understand most of it I think. I can't figure out why the user is apparantely offline though.

if #playernamelist > 1 and att.Value > 2 then
				
	joinlist = {playernamelist[1], playernamelist[2]}
	table.remove(playernamelist, 1)
	table.remove(playernamelist, 1)
				
	id = joinlist[1].UserId
			
	local match = game:GetService("AssetService"):CreatePlaceAsync("2 player match", 243740040)
				
	print(match)
				

				
	wait(5)
			
	local connection = joinlist[1].OnTeleport:connect(function(teleportState, placeId)
	if teleportState == Enum.TeleportState.Started then
		local teleportStarted = os.time()
		-- Keep checking if playerA has arrived in other instance.
		wait(3)
		while true do
			local success, error, placeId, arenaInstanceId = teleportService:GetPlayerPlaceInstanceAsync(id)
						
			print(success)
			print(error)
			print(placeId)
			print(arenaInstanceId)
						

						
			-- If playerA is in the correct place then we can teleport playerB there as well
			if placeId == 243740040 then
				teleportService:TeleportToPlaceInstance(placeId, arenaInstanceId, joinlist[2])
				return
			end
			wait()
		end	
	end
end)
wait(1)
 		
	-- Teleport playerA to the arena
	teleportService:Teleport(243740040, joinlist[1])
				
	att.Value = 0
				
end

I've managed to get this fixed myself eventually: This error seems to happen before the new place starts loading but after the place got requested. In order to fix this I use pcall to keep trying to join, igoring the error. This eventually properly returns the instance so you can make players join the same game.

Here is the code that is fixed, do note that it has some indenting errors as this is in the middle of the script.

if #playernamelist > 1 and att.Value > 2 then
				
				joinlist = {playernamelist[1], playernamelist[2]}
				table.remove(playernamelist, 1)
				table.remove(playernamelist, 1)
				
				id = joinlist[1].UserId
				
				)
			
				local match = game:GetService("AssetService"):CreatePlaceAsync("Bomberblox 2 player match", 243740040)
				
				print(match)
				
				
				
				
			
				local connection = joinlist[1].OnTeleport:connect(function(teleportState, placeId)
				if teleportState == Enum.TeleportState.Started then
					local teleportStarted = os.time()
					-- Keep checking if playerA has arrived in other instance.
					
					wait(5)
					
					while true do
						
						pcall( --Then let's just force it.
						function()
						local success, error, placeId, arenaInstanceId = teleportService:GetPlayerPlaceInstanceAsync(id)
						
						print(success)
						print(error)
						print(placeId)
						print(arenaInstanceId)
						
						--workspace.Message.Text = "success: " + tostring(success) + ". error: " + error + ". placeId: " + tostring(placeId) + ". Instance: " + tostring(arenaInstanceId)
						
						-- If playerA is in the correct place then we can teleport playerB there as well
						if placeId == match then
							teleportService:TeleportToPlaceInstance(placeId, arenaInstanceId, joinlist[2])
							return
						end
						
						end)						
						
						wait(1)
					end	
				end
			end)
			wait(1)
 		
				-- Teleport playerA to the arena 
				teleportService:Teleport(match, joinlist[1])
				
				att.Value = 0
				
			end