This happens numerous times for my friend Terrorfex. Can't join other people's fireteam's, nor can anybody else join his fireteam. He used to have good connection to the game until he stopped playing it for a bit, then came back and this crap happens. Expect better from you bungie if your reading this. He can't do what he used to do anymore. And THIS is why bungie loses customers! The "Hot Fix" crap became nothing but dust. I kinda recommend if you play the xbox one destiny, that you shut your xbox off completely, unplug the power cord from both the power box and from behind your console and let it sit there for 6 minutes so corrupted data can be replaced with new ones entirely, plug the power cord back into the power box and from behind the console, turn the console back on and relaunch destiny. If it occurs again, follow Bungie's Troubleshooting Network Guide and follow it well. Hope it runs better.