Stuck in Act 4

All islands cleared.
i only have 2 quests
Fate of the Vaal wants me to locate the royal architech. not sure how i am suppose to do that at lvl 56. I am sure i will need to get to maps before i can do that. so not sure why that quest is annoying me right now.
the other is The Runeseeker. it tells me to go to plunders point, and then go to deserted post. but there there is nothing at plunder's point. no door, no exit, no daligue, no way to advance this storyline. and i think the mainstory is locked behide this so i am just stuck here on this.