No WatchTower on Tirn Ends

Hi

I have one problem with watchstone towers, i can't find the one belonging to Tirns End

Obviously without it I cannot put watchstones to level up the area and i can't beat the conquerors



I tried various combinations with the stones that I already have and making several maps of Tirns end but it hasn't worked.

Does anyone know what can be due? and do you have any solution for it

You need to do some T3 maps in that region and after you kill a boss a portal appears which leads to an abandoned citadel, you need to enter the portal to actually unlock the citadel.