NPE map directions
This is nothing to do with living story content or the state of Lion’s Arch. That gate is one of 3 (one in each Order’s headquarters) that leads to Fort Trinity. But for the sake of continuity they don’t become accessible until your character plays through the storyline where Fort Trinity is established (level 70 I think).
The problem is that the content guide was programmed to take asura gates into account (which is normally really useful) but doesn’t seem able to factor in whether those 3 gates are accessible to you or not.
The work-around is to look at where you’re being sent and find an alternate way of getting there. In this case the description says you need to go to Lion’s Arch, so if you go there it should start pointing you to the actual location of the instance.
“Life’s a journey, not a destination.”
Actually, the story ‘guide’ sent you there even before the ‘content direction guide’ was implemented. It’s a long-known anomaly, that the green star would end up at one of those gates in certain storylines, or from certain areas on the map.
As noted above, just take an alternate route to Lion’s Arch or wherever your storyline leads you.
Good luck.