I completed 5 radiant quests/jobs for Delvin/Vex and completed all 4 special quests (Silver Lining, Summerset Shadows, The Dainty Sload, and Imitation Amnesty) but I still haven't gotten the Under New Management quest. I equipped the Thieves Guild armor and tried talking to Bryjnolf but he just says he's busy. I did about ten more jobs and no new quests came up. I checked in my completed quest and I have completed the special quests. I don't know if I'm missing something or it's a glitch.
I think what I need to know is how to get either Blindsighted or Under New Management but I'm not sure how to start a new possible quest. I don't know about the thieves guild main quest line and where I am on that but I need help to progress to get the final quest for the Skeleton Key and becoming the leader of the Thieves Guild. I have not met Karliah if you might have asked but I'm not sure what I do to meet her or continue on the main questline for the thieves guild.
So I'm basically trying to progress forward in the Thieves Guild so I can become a Nightingale. (I believe i am on the next quest in the main quest line after "Loud and Clear") but I can't seem to and if anyone can help me it would mean a lot. Use my information that I gave to help you.