I know almost nothing about map making, and I don't actually know if this will even help or not, but sometimes when I go to download maps, there are times when I actually put the portal to the map in the wrong folder. I usually find it and I drop it in my textures folder. But I don't actually know if that will work for you or not. And I may have just totally said the wrong thing and did more harm than good.
Ah! xD Well glad that I managed to remind you of that with my post. xD