Can't become leader of the Thieves Guild in Skyrim/Xbox One

I just finished all the special quests for each of the holds of Skyrim, and the quest "Under new Management" does not appear.

I am at the quest "Darkness Returns" of the principal arc.

Brynjolf keeps ignoring me every time i try to talk to him.

How do I proceed to become the leader of the Thieves Guild?

You need to complete the quest Darkness Returns as it is listed as a prerequisite for the Guild Master ceremony Under New Management.

Once you have completed all of the reputation quests and Darkness Returns, you will be told to talk to Brynjolf about becoming the new Guild Master.