Anyone using the Dragon Armor

no

I need help! When I try to join the Thieves Guild I cannot get the "Loud and Clear" quest to start.
I completed "Taking Care of Business" with no problems whatsoever but when I talk to Brynjolf
he doesn't not give me the quest. He says to follow him to the Cistern to talk to Mercer, and I follow.
But the quest does not start... Brynjolf doesn't has the quest marker above his head and whenever
I enter the Cistern with him he just stops and says "Hmm?". After a while, him and the other members
become hostile to me because I'm trespassing (it says so when I try to wait).

I've loaded an older save, when I was on my way from Windhelm to Riften and started the quests
from the beginning (meet Brynjolf at the market) but that didn't seem to have fixed it.