I am on the quest for vault 79. The quest is called “All that Glitters”. The motherboard has burrowed inside and the quest objective is telling me to meet Jen at the laser grid. I am standing right next to her and the quest icon is right there but it isn’t detecting that I am here.
I am playing in Xbox one if this makes a difference.
This happened to me too. I fast traveled to my camp and then back to the quest location. When I made my way back through the tunnel, Jen was inside at the computer and the quest updated for me.
I have seen other people say that turning the game off and on fixes it. You just have to make sure all of the people coming with you down the tunnel make it and don’t get stuck along the way.
When I got back the second time, a man appeared out of nowhere. He was the military guy. He might have gotten stuck in the mines and unstuck when I returned.