I have connected to the VPN successfully but I can't ping / scan any of the machines (Active or Retired). (I can't see any start/stop buttons next to machines).
Please navigate to your access page here: Access and make sure you're not connected to Starting Point or Fortress. The machines in Starting Point are separated from the main ones and in order to reach the Active or Retired machines again, you will need to switch servers to one of the main ones, VIP or Free.