Good to know you got it to work. It needs to be pointed out though that the Singularity Reactor is a trial battle, not a dungeon. Although in your case I think there must have been some glitch that didn't trigger the cutscene that is meant to play before it flags the trial battle as unlocked when you did the Aetherochemical Research Facility the first time. At least you got past it so that's the main thing.