Private Server Teleport not working?

I made an UI where you can invite players to play togheter. I used LocalScripts, that didn't work. Then i used a RemoteEvent to teleport the party to a private server. Heres my code:

LocalScript inside the player gui:

local second
local third
local fourth

-- A lot of if-then-elses here

script.Parent.Start.MouseButton1Click:Connect(function()

    print("START")
    game.ReplicatedStorage.TeleportEventw2a:FireServer(second, third, fourth)

end)

ServerScript inside the ServerScriptService

game.ReplicatedStorage.TeleportEventw2a.OnServerEvent:Connect(function(player, second, third, fourth)

    local players = {player, second, third, fourth}
    local code = game["Teleport Service"]:ReserveServer(3315989953)
    game["Teleport Service"]:SetTeleportGui(game.ReplicatedStorage:Clone())
    game["Teleport Service"]:TeleportToPrivateServer(3315989953, code, {players})

end)

The console writes out HTTP403(Forbidden), and noone gets teleported. Where's the problem?