Today (1/11/17), my death wizard's daily assignment was to visit a location to which I do not have access. I went back a few times to see if, perhaps, this was a bug, and might reset, to no avail. Has this happened to anyone else? And will KI address this soon?
It's very common for someone to have an assignment that exists in an area that they cannot reach. There is no remedy for this at the time other than waiting for a new assignment tomorrow, unfortunately. Personally, I have not had this problem just yet, but we'll see what the future holds, right?
If you are over-leveled (did all the side quests plus dungeons), then you might be able to go somewhere "on paper" even though you didn't open the area through questing. I have a wizard who is level 58 because she went thru Wintertusk right after Mooshu, yet she is only 1/3 thru Dragonspyre. Because of that, the Daily Assignments sometimes send her to the Crystal Grove or other areas of Dragonspyre that she hasn't opened through questing yet.
In the case of Dragonspyre, there's a way to get to most areas even if you haven't quested very far. You can get almost anywhere by starting in the Atheneum. From there, go into the Plaza of Conquests, pass thru there to the Necropolis, and then through the Crucible to reach Dragonspyre Academy. The three bolded areas are hubs that branch off into other areas. Check your maps to guide you.
Dragonspyre is special that way. Any other world, the only option is to ask a friend to port you into the new area.
Also know that skipping a day won't hurt. You can just pick up right where you are tomorrow.