I forget the name of the map type, but it's the one where you have to loot all the items from the boxes, it was a legendary map. If you have your loot filters you can't loot everything that drops so the portal won't open to let you out. I didn't want to go in and turn off all of my loot filters, so I just quit the game but that doesn't seem like a good work around. Feels like the portal should open once you have opened all the boxes.