As part of update 18.104.22.168, Bungie split off errors previously grouped under other errors into different categories in order to make it easier to understand the specific issue the player is experiencing. This process will help us expedite investigations and fixes.
If you are seeing this message, you are having trouble connecting to or maintaining a connection to Destiny matchmaking servers. If this is the first time you've received this error, please try again and resume what you were doing before the error occurred. This error can also be hit if you log out of your account while Destiny is running. If you encounter the issue a second time, please exit Destiny and relaunch the game.
If you are hitting this error repeatedly, or it is preventing you from playing it may be necessary to make sure your network isnt blocking your ability to connect. Depending on your home networking gear, you may need to set up some port forwarding or adjust your NAT type to have a better experience. More information on this subject can be found at http://bungie.net/NAT or here.
For more general networking troubleshooting please head here: Network Troubleshooting Guide.