Im in the middle of doing this quest and managed to convince janets boss to let her leave
Anyway I then go and tell Janet that she can go to nelis so I fast travel there expecting to find both of them but their not there
I look on the map and find the indicator saying that there in the middle of black mountain
So I head there and find them by the big satellite dishes and invisible Walls preventing me from getting to them
So am I now unable to complete this quest or do I have to start a new character and do another 20hours to get there?

This best be fixed in a patch

if you have already told her she can go (she was in the caravan field) then you dont have to speak with her again, just find jack. When i did it, she was stuck inside a mountain as well, but jack was in the nellis hanger (when i found him, they were both there)

No they are both stuck there at the mountain which means I can't speak to him due to the invisible Walls