Using nothing but standard fortnite prefabs when I use the navigation debug I can see it does not reach the second floor. I’m using fortnite snapping in the editor and have a guard spawner in the level (which is the base empty level template) If I bring in a playset that has stairs the navigation works in that playset. image attached to show what I’m seeing in the game.
Am I missing something? This is kind of driving me crazy!
Figured it out, just my luck that I used a floor from Hexylvania that for some reason is completely ignored by the navmesh. I replaced it with a series of random floor parts, and it worked just fine for all of them. There must be a bug with this particular asset, which is annoying given it is labeled FLOOR. That one cost me a few hours to sort out 
UEFN screen grab of the possibly bad asset for future reference.
