There are a few possibilities: 

  • A robot can only be connected to one Choregraphe session at a time.
    Make sure no one is already connected to your robot with Choregraphe. 
  • Make sure your Choregraphe version is the same as the NAOqi version.
  • Make sure NAO and your computer are connected to the same Network.
  • If NAO has not been correctly disconnected from the last Choregraphe session, you will get an error message.
    Just reboot NAO to solve this issue.