I have reached Tier V on New Romulus and have acquired the mission to go to the Underground Ruins and then to signal D'Tan when the final room is clear. I have gone to Underground Ruins Transport point but cant seem to find out where to go from there? Can someone please help.
Once you complete the Underground Ruins mission, stand in the last room (the one where you fought the Tholian Captain and tried to shut down the power plant). You should have a prompt to signal D'Tan if you have "Secrets of the Ancients" in progress.
This is something I kind of find to be a nuisance as well. I had the tier 3 mission in the caves, so I went in and cleared the basic NPC mission, and didn't realize until the mission was turned in and I had already left the caves that I hadn't yet completed the tier 3 mission itself. I had to wait for the 24 hour cooldown to go back into the caves because you can't enter unless you're on the basic NPC mission.