I did everything I have to but it won't let me in The Necropolis .
If this is the "Explore the Necropolis" quest, read the "?" dialogue bubble in your quest log for it.
The first time that you enter the Necropolis, you go to the Plaza of Conquests and use the large double dragon doors. Look at your map and you will see them at the top of the map in the Plaza of Conquests.
After this first visit, then you can use the regular portal to enter the Necropolis.