I was trying to obtain the xenophage weapon last weekend, but the quest would not progress. I was at the "Path Uncovered" part where I needed to interact with the rune plate in the Pit of Heresy but there was no interaction button that appeared. I reloaded in, reset my checkpoint, and even tried it solo (i was doing it with somebody else on the quest step) but it refused to work. Every time I approached the plate, no button would pop up telling me to interact. Very frustrating. :(