Can you tell me the choices you made beforehand? I can't seem to get the mission no matter what I tried lol
Like I said it's been a while but what I do remember is using cheats for resource, getting all facilities, having high number of troops, having high military skills, and having high ship's health so that I only pass the time by either doing missions or spending time with LI.
I do all the missions first then spend time with LI, gets called by High Sovereign, gets back and then do the new missions and then spend time with LI again. Over and over until the game ends. Also always try to be the "good guy" by not resorting to violence whenever possible.